Welcome to the Q&A Forum

Thanks Peter for your response.

One of our sites had issues previously, bad links. We went through the disavow procedure months ago, but no change in rank until yesterday - up about 28 spots, broke the #50 barrier, all since the update.

Thanks John, I check the robots.txt redirect and it is redirecting fine from the non-www version to the www version. I also know that G is crawling the site because we can see requests by G in the server log. Also as with the case with the other 301 redirects there were cases G followed the 301 redirect on the robots.txt file but also many cases where it didnt.