Not seen any film at all in Tesco. Sainsbury, Morrison or any of the big supermarkets for at least a year (used to look for any cheapy end-of-range stuff, but even that has gone).
Boots may have some color neg (in an emergency), but have not seen any Ilford in our local branches for a year or so.
£1-a-roll Agfa Vista 200 is sometimes in Poundland, but don't rely on them having stock.
Best follow others advice and organise something via mail order, then you'll get exactly what you want without wasting time.
Edit - Royal Mail offer a "guaranteed next day delivery" service, but the postage is relatively expensive.