I once made gravadlax. Not much work, just need room in the fridge. It was very nice and cheap to make.
btw, I don't think there is a kosher/jewish deli in Twickenham.
Edit: but there is Sandy's fish monger ..... they might have something good.
That's exactly what I do. It's very much fish on Xmas eve here chez Casa Reynard.
I buy half a side of salmon (that's 500g of fillet in Tesco - on YS of course LOL) and then cure it a la Hairy Bikers from their "12 Days of Christmas" book. Well worth doing and so much nicer than anything you can buy. And cheaper. You pay around £4 for 150g of cured / smoked salmon, and for £7.90 (that's what half a side is in Tesco) you will have more than enough to eat your fill without being stingy.
All you need to do is work out the proportion of salt, sugar and pepper according to the weight of your fish, and then you can tweak the rest of your curing mix to suit your tastes. I usually use dill and some ground cumin as well., though you don't have to. If you do it straight away, you'll have it ready for Xmas.