I've often gone down the same route that Paigntonian is suggesting and bought cooked turkey breast from the cold meat counter in Morrison's. (I'm referring to the proper 'carved from the bone' stuff here, not the inferior turkey roll slices).
Although I've got a frozen ready meal (beef in brandy sauce) for tomorrow's lunch, I might still nip along to Morrison's to see if they've got any cooked turkey left later this afternoon. (If past year's are anything to go by, they'll be selling it for well under half the regular price, just to get rid of it!).
A tip for heating it up: Wrap it in foil, together with some butter, to prevent it drying out.