OK! I just finished my meal and it was success in most of it.
Some points though:
1) the salmon fillet from the tescos fishmonger was not symmetrical with the same thickness. The belly of the fish was thin and the rest fat, which troubled me if it will cook properly. It mostly did, but I would like to have a same thickness piece.
2) tescos sell
these (their personnel didn't have a clue, I found it myself) which worked very well! although if they could be fixed in the grill it would be better as they are quite difficult to handle due to their slipperiness
3) the weight of the grill made the salmon tear apart, but due to the skin, not completely
4) there were some 2-3 per 250g bones, so pretty acceptable
5) the major problem was with the scales of the fish: I don't understand how they don't de-scale the fish before sell it. I asked the fishmonger to do it but she didn't do a good job. Scales are disgusting.
So, so far success, now I will try with a white fish, any suggestions?