Thank you Jalima. Sorry for the delay but I had family at the weekend and you know what that's like. No chance of coming on the laptop.
It was really successful! When I unwrapped the fish, the pieces were huge. I fact I had to cut a piece off one of them it just looked too much. The lady in Waitrose was not very helpful and when I asked for four fillets she was giving me four loins. Fortunately, I stopped her in time to have three, thinking I would cut the biggest one in half. You may gather I'm not used to buying fresh fish. Anyway, I added some Parmesan cheese, as suggested by Riverwalk, and there were four clean plates at the end.
Once again, thank you for all the help.