Hake is lovely. It's used a lot on Spanish cooking. It's delicate in texture and flavour and quite fragile to handle, so best to cook it simply. I like to do it either steamed in a foil parcel (I cook a lot of fish that way) or rolled in streaky bacon or cured ham with a couple of sage leaves tucked inside.
I adore monkfish. It's very firm, so a good candidate for fish stews / curries / kebabs, but I like to roast it in the oven, giving it the old "wrap it in bacon" thing again.
Coley, ling and whiting are your all-round basic white fish very much in the mode of haddock and cod, though the flakes are somewhat smaller. Good to use in curries, fish pies etc, or battered and deep fried a la chip shop. It's cheaper because it's seen as less desirable (coley can look slightly greyish when raw) but there's nothing wrong with it at all.
Lemon sole is lovely just pan-fried in butter. It's firmer than plaice but not quite as firm as Dover sole, which is a tad more pricey. Worth it if you like the latter but can't be doing with coughing up the cash.
Ray is skate - so you eat the wings, well, scrape the flesh off the cartilage. Again, I absolutely love this fish, it's just so good. Cook's tip is to oven bake the fish with butter in a non-stick roasting ton rather than attempting to pan fry - just makes life a LOT easier.
Halibut is a big flat fish, good too, but even better cold smoked.
