Thanks for your reply. I have not tried bleeding them yet, but the plan is to do that today before I phone an engineer! It is a back boiler, and so far I have not even seen it (!) as the boiler and pump are behind my chimneybreast and I would have to take off a panel on the side to get to them...
I have only lived in my house since April, and have now got a problem with my central heating. It was working fine when we first moved in, then we haven't used it all summer, and now that I wanted to turn the heating on the following happens: 2 of the upstairs radiators are hot, but all the...