Ha, welcome. How are things over on your side of the pond?
Anyway, I think you've got it mostly figured out. I think one might want to opt for a higher-up model of a receiver, due to the large size of the room.
Have you also considered Yamaha (don't know about pricing over there...it might be atroicious)? The Yamaha receivers in the RX-V line are known to have very good preamp outputs, allowing your chum Frankie to still utilize his monoblocks with the AV system. As far as integrating the preamp, I don't think that's going to work without a switch box (switcing between the Rega Pre and the AV pre outs going to the monoblocks).
And the only other thing I didn't see was a subwoofer. If your friend is serious about a home cinema, a subwoofer is a MUST. There is no getting around it. Unfortunately, I don't think the high-value subwoofers we can get here in the States (SVS and HSU) are available there... If this were a music only system, you might consider REL, as they are high quality, AND you'd be supporting a business at home. But alas, you'd have to spend quite a bit to get the output and depth needed for that room and theatre application.
However, Axiom Audio has recently started selling in the UK. Their products are also high value. Your friend might want to look at their
EP500 subwoofer. It received rave reviews here at Audioholics and is £717, shipping included.
As far as the projector goes, the InFocus is a popular choice at that price, as is the Optoma H31. Has your friend considered the cost of a mount, cabling, and screen as well?
And one last question, what is a "Pure DAB of some kind"?
Whew.