I was in there the other week, buying a wedge of 24 month-aged Parmigiano Reggiano for £14.45/kg (which is a few quid cheaper than I can find elsewhere) and, while there, also picked up a kilo bag of frozen Alaskan pollock for £3.99. Which equalled (at least in the bag I bought) eleven fillets. Pollock is what the recipe term 'or use any firm white-fleshed fish' was invented for, a great substitute for cod. I bought it, initially, to use in this stew; but it makes for an excellent fish cake - especially if you poach it with a few aromatics. I've used bay, peppercorns, parsley stalks and vinegar here, but use whatever is handy.
The other night I made a dill and mustard sauce to go with this, because I can get a bunch of dill from Khan's for 69p. Tonight, though, I'm nestling the fish cakes in a bowl of this lentil stew.