Wow, great response, far more replies than I was expecting, thanks one and all.
It looks like HobbyWeld are definitely worth investigating. As a plus their agent is SW of Cambridge and I'm west of Cambridge, so easier to get to. If nothing else it doesn't involve the A14 (massive multi-year roadworks) and the A10 (jammed solid most days). I'm doing quite a lot of heating for metal flanging at the moment. So I thought it might be worthwhile buying a proper heating nozzle rather than the cutting head I'm currently using. Looking to buy might be an excuse to visit the agent and assess their competence and demeanour.
DaveW is correct, Adams only serve the south east. I had a leaflet from them, but it was picked up at a traction engine meeting in Hampshire. They don't seem to do acetylene either.
SGS look interesting, although they don't seem to do acetylene either. Their nearest practical outlet is Royston. They've got a couple of places in Cambridge. But trust me, it'd be quicker to get to Royston!
Clive has raised some interesting points. I've got a while to run on my existing agreement so that gives me time to look around. Pricing is important, but not key. I'm always getting letters from Air Liquide increasing prices, and I don't suppose anyone else is going to be any different. I'm not averse to the Albee system, just the clowns who masquerade as the agents!
I've looked at propane and the other fuel gases that are less dangerous than acetylene; the issues are all to do with the triple bond according to my brother, who is an organic chemist. I think the alternatives would be fine for heating, not sure about cutting but for welding I get the impression that the suppliers are putting on a brave face to cover the fact that the flame simply isn't as hot as oxy-acetylene. I'd also have to buy new mixers and possibly nozzles if I changed. I've also read that the propane fuels use a lot more oxygen. Whereas at the moment, for heating and welding both bottles seem to empty at roughly the same time. Obviously cutting uses way more oxygen, but I don't do that very often.
Once again, thanks for all the helpful responses. I'll update the saga with Air Liquide next, in a separate post, in case I lose the typing so far.
Andrew