Ok, so creating my google sitemap didn’t help due to a setting I had already setup in WordPress. When I was testing the migration I had set the privacy options under Settings/ Privacy to block search engines but allow other visitors. This had the unfortunate result of adding the disallow * in the robots.txt file – thus blocking google. Setting it back to make my blog visible has (hopefully) done the trick. Note that the robots.txt is automatically generated by wordpress so you not find one if you go looking with shell access – just access the file through a browser.
Hopefully this setting has not harmed by Google Page rank too much.
Update – just checked and my posts are now appearing in Google again – phew!