diff --git a/meta/classes/populate_sdk_ext.bbclass b/meta/classes/populate_sdk_ext.bbclass
index 4ef8838..b9808bb 100644
--- a/meta/classes/populate_sdk_ext.bbclass
+++ b/meta/classes/populate_sdk_ext.bbclass
@@ -51,7 +51,7 @@
     core_meta_subdir = ''
 
     # Copy in all metadata layers + bitbake (as repositories)
-    buildsystem = oe.copy_buildsystem.BuildSystem(d)
+    buildsystem = oe.copy_buildsystem.BuildSystem('extensible SDK', d)
     baseoutpath = d.getVar('SDK_OUTPUT', True) + '/' + d.getVar('SDKPATH', True)
     layers_copied = buildsystem.copy_bitbake_and_layers(baseoutpath + '/layers')
 
@@ -155,10 +155,16 @@
         f.write('NATIVELSBSTRING_forcevariable = "%s"\n\n' % fixedlsbstring)
 
         # Ensure locked sstate cache objects are re-used without error
-        f.write('SIGGEN_LOCKEDSIGS_CHECK_LEVEL = "warn"\n\n')
+        f.write('SIGGEN_LOCKEDSIGS_CHECK_LEVEL = "none"\n\n')
+
+        # If you define a sdk_extraconf() function then it can contain additional config
+        extraconf = (d.getVar('sdk_extraconf', True) or '').strip()
+        if extraconf:
+            # Strip off any leading / trailing spaces
+            for line in extraconf.splitlines():
+                f.write(line.strip() + '\n')
 
         f.write('require conf/locked-sigs.inc\n')
-        f.write('require conf/work-config.inc\n')
 
     sigfile = d.getVar('WORKDIR', True) + '/locked-sigs.inc'
     oe.copy_buildsystem.generate_locked_sigs(sigfile, d)
@@ -178,17 +184,10 @@
                                                    d.getVar('SSTATE_DIR', True),
                                                    sstate_out, d,
                                                    fixedlsbstring)
-
-    # Create a dummy config file for additional settings
-    with open(baseoutpath + '/conf/work-config.inc', 'w') as f:
-        pass
 }
 
 def extsdk_get_buildtools_filename(d):
-    # This is somewhat of a hack
-    localdata = bb.data.createCopy(d)
-    localdata.setVar('PN', 'buildtools-tarball')
-    return localdata.expand('${SDK_NAME}-buildtools-nativesdk-standalone-*.sh')
+    return '*-buildtools-nativesdk-standalone-*.sh'
 
 install_tools() {
 	install -d ${SDK_OUTPUT}/${SDKPATHNATIVE}${bindir_nativesdk}
@@ -201,6 +200,8 @@
 	install $buildtools_path ${SDK_OUTPUT}/${SDKPATH}
 
 	install ${SDK_DEPLOY}/${BUILD_ARCH}-nativesdk-libc.tar.bz2 ${SDK_OUTPUT}/${SDKPATH}
+
+	install -m 0755 ${COREBASE}/meta/files/ext-sdk-prepare.sh ${SDK_OUTPUT}/${SDKPATH}
 }
 
 # Since bitbake won't run as root it doesn't make sense to try and install
@@ -218,29 +219,37 @@
 sdk_ext_postinst() {
 	printf "\nExtracting buildtools...\n"
 	cd $target_sdk_dir
-	printf "buildtools\ny" | ./*buildtools-nativesdk-standalone* > /dev/null
+	printf "buildtools\ny" | ./*buildtools-nativesdk-standalone* > /dev/null || ( printf 'ERROR: buildtools installation failed\n' ; exit 1 )
 
 	# Make sure when the user sets up the environment, they also get
 	# the buildtools-tarball tools in their path.
-	echo ". $target_sdk_dir/buildtools/environment-setup*" >> $target_sdk_dir/environment-setup*
+	env_setup_script="$target_sdk_dir/environment-setup-${REAL_MULTIMACH_TARGET_SYS}"
+	echo ". $target_sdk_dir/buildtools/environment-setup*" >> $env_setup_script
 
 	# Allow bitbake environment setup to be ran as part of this sdk.
-	echo "export OE_SKIP_SDK_CHECK=1" >> $target_sdk_dir/environment-setup*
+	echo "export OE_SKIP_SDK_CHECK=1" >> $env_setup_script
 
 	# A bit of another hack, but we need this in the path only for devtool
 	# so put it at the end of $PATH.
-	echo "export PATH=\$PATH:$target_sdk_dir/sysroots/${SDK_SYS}/${bindir_nativesdk}" >> $target_sdk_dir/environment-setup*
+	echo "export PATH=\$PATH:$target_sdk_dir/sysroots/${SDK_SYS}/${bindir_nativesdk}" >> $env_setup_script
+
+	echo "printf 'SDK environment now set up; additionally you may now run devtool to perform development tasks.\nRun devtool --help for further details.\n'" >> $env_setup_script
+
+	# Warn if trying to use external bitbake and the ext SDK together
+	echo "(which bitbake > /dev/null 2>&1 && echo 'WARNING: attempting to use the extensible SDK in an environment set up to run bitbake - this may lead to unexpected results. Please source this script in a new shell session instead.') || true" >> $env_setup_script
 
 	# For now this is where uninative.bbclass expects the tarball
 	mv *-nativesdk-libc.tar.* $target_sdk_dir/`dirname ${oe_init_build_env_path}`
 
 	if [ "$prepare_buildsystem" != "no" ]; then
-	    printf "Preparing build system...\n"
-	    # dash which is /bin/sh on Ubuntu will not preserve the
-	    # current working directory when first ran, nor will it set $1 when
-	    # sourcing a script. That is why this has to look so ugly.
-	    sh -c ". buildtools/environment-setup* > preparing_build_system.log && cd $target_sdk_dir/`dirname ${oe_init_build_env_path}` && set $target_sdk_dir && . $target_sdk_dir/${oe_init_build_env_path} $target_sdk_dir >> preparing_build_system.log && bitbake ${SDK_TARGETS} >> preparing_build_system.log" || { echo "SDK preparation failed: see `pwd`/preparing_build_system.log" ; exit 1 ; }
+		printf "Preparing build system...\n"
+		# dash which is /bin/sh on Ubuntu will not preserve the
+		# current working directory when first ran, nor will it set $1 when
+		# sourcing a script. That is why this has to look so ugly.
+		LOGFILE="$target_sdk_dir/preparing_build_system.log"
+		sh -c ". buildtools/environment-setup* > $LOGFILE && cd $target_sdk_dir/`dirname ${oe_init_build_env_path}` && set $target_sdk_dir && . $target_sdk_dir/${oe_init_build_env_path} $target_sdk_dir >> $LOGFILE && $target_sdk_dir/ext-sdk-prepare.sh $target_sdk_dir '${SDK_TARGETS}' >> $LOGFILE 2>&1" || { echo "ERROR: SDK preparation failed: see $LOGFILE"; echo "printf 'ERROR: this SDK was not fully installed and needs reinstalling\n'" >> $env_setup_script ; exit 1 ; }
 	fi
+	rm -f $target_sdk_dir/ext-sdk-prepare.sh
 	echo done
 }
 
@@ -249,6 +258,11 @@
 SDK_POSTPROCESS_COMMAND_prepend_task-populate-sdk-ext = "copy_buildsystem; install_tools; "
 
 fakeroot python do_populate_sdk_ext() {
+    # FIXME hopefully we can remove this restriction at some point, but uninative
+    # currently forces this upon us
+    if d.getVar('SDK_ARCH', True) != d.getVar('BUILD_ARCH', True):
+        bb.fatal('The extensible SDK can currently only be built for the same architecture as the machine being built on - SDK_ARCH is set to %s (likely via setting SDKMACHINE) which is different from the architecture of the build machine (%s). Unable to continue.' % (d.getVar('SDK_ARCH', True), d.getVar('BUILD_ARCH', True)))
+
     bb.build.exec_func("do_populate_sdk", d)
 }