Sashimi grade tuna?

[Tinkjon]

Can I buy this anywhere in the UK? And can you really trust that it is sashimi grade?

You need to find a fishmonger you can trust. If you are near big city, I would suggest going to the fish market and speaking to the suppliers. Both Leeds and Birmingham markets have wonderful fish with stallholders who know their stuff.
i live in a small town and the fish market is rubbish. All the fish hitting them is 2 or 3 days old. However I have found one guys who has market stalls and supplies to restaurants. His stuff is wonderful and I know he will supply me with really fresh fish. If you're in the East Lancs/West Yorks area I can pass it on?

Nowhere near me but thanks anyway Maybe I'll give Billingsgate a try...

Oh yes, that will be THE place. Lucky you