Doon,
Come to think of it, MHB told me to replace the 40 degree hydration rest to a 32c rest which i did for 20 mins, it wasnt circulating during this time. I mashed in and every 5 mins for 20 mins would give it a good mash paddling. Then i put the filter on and started her up. He also said to check it during the mash (as you know with a BM it needs little attention whilst in operation) to check it to make sure it was pumping good. If not, press pause, remove cross bar and filter and give the malt a stir. I didnt have to do this, she ran sweet and the wort went from white to quite clear.
Hope this helps.
Dan