TIm, I have used both of the companies Andy has mentioned and they have always been fairly quick with deliveries.  I could do with a couple of Nobby Nic tyres, so if the postage is expensive and it works out cheaper to order several and split the P&P costs let me know.

Dave, in my experience, Racing Ralph tyres are very good in dry hard conditions, but can be a bit slippy when it is wet.  Definitely go for the snakeskin side walls, I have found the side walls very fragile on the standard ones.