Got a trap from my local fishing shop and it looks like this
http://www.castnets.co.uk/prawn-creel
I got a 10m washing up line and an 8 oz weight to sink the trap. Tested it this morning on a short fishing trip. I used a piece of mackrel, was fresh and not off(smellier the better) I managed to catch a dozen crabs of various sizes, not all were inside had two trying to eat the fish through the mesh. Would recomend this to anyone who goes fishing, it collapses down so it takes up hardly ny room and catches crabs and posdibly lobsters in the right location. Crabs I caught had hard she"s, peeler crabs make good bait. Never actualy eaten crab so if I catch some decent sized ones I will defo eat em.