OK I thought, I'll just have to live with that, and they said they'd use the lowest they had. But the whole thing has cost me 30 quid, 10 quid of that is the cost of the chain and seems about market price, 20 quid for the block seems expensive though given the only ones I can find on the web only cost about a fiver! And the bottom gear is now about halfway between what was 2nd and 3rd on the old block and not really as low as I'd like, and is almost indistinguishable from the new 2nd gear anyway. What's the point of having them so close together when you could have made the bottom gear a bit lower and had a more sensible spacing?
I've been out to peer at it and it is a Shimano one, which doesn't surprise me at all. It's a 14-28T one, and I can't seem to find anything better than that (ie with the top number bigger than 28) on the web at all, or not in 5-speed. I dunno if they come in some versions more expensive than others but the standard Shimano one on the web seems to be about 6-8 quid most places, so to pay 15-20 for it (I'm not sure how much I paid for the work) seems an enormous markup. I think I'm going to give them a ring on Monday and ask.
I've asked the combined wisdom of uk.rec.cycling if they know of a source of more widely spaced freewheels anywya, but I don't hold outmuch hope.