By far the best arbitrage opportunity looks to me to be buying ecstasy for 1 quid a pill in Cardiff and selling it for a fiver a pill in Bristol. Cocaine and crack are cheaper in Bristol if you felt that you must take something back with you, with crack at 12.50 for 0.2 g in Bristol and 11 quid for 0.1 g in Cardiff.
If you were prepared to drive as far a field as Gloucester to buy you could sell anything in Bristol at a profit except ecstasy. Unaccountably no price is given for cannabis resin in Gloucester, maybe it is given away at school with the free milk, or maybe there is no call for it given the bargain basement heroin, crack and coke.
