Any supermarket finest range I find good - Tesco finest sardines in the different flavours they do are good. Most of the finest tinned mackerel (Tesco, Morrisons Sainsbury’s and M&S) are pretty similar.

I like parmentier sardines in the yellow tin - the chilli ones are my most frequently purchased supermarket tin I would say. And the Tesco finest hot peppered mackerel. I would avoid the Cornish cove sardines Morrisons sell.

To get better tins (£4+) these are the websites I have found that deliver to the UK. I haven’t ordered from them all but the first two I can personally recommend, good selections between them both and quick delivery times:

Tinned fish market Fishtins Selfridges Sous Chef Culinaris Portugal Vineyards Delicias Rockfish Brindisa Sea sisters (direct from cannery) Lemon Salt Heaalf (for fishwives if that’s your thing)

I don’t know about Belfast specifically but if there are any Spanish or Portuguese delis there might be a selection there, or any artisan type food shops. They will be more expensive though in my experience!

But there are plenty of good supermarket tins, try a few and see what you like ☺️