Been speaking to Mark Humphreys from PTS who is now on the board at The Tile Association and he tells me the benefits include the insurance and the simple fact that you are a member of the association.
Obviously the main thing here is the length of time you've been working. They'll allow you to join if you have an
NVQ and Mark is working on trying to get some sort of teir perhaps where there could possibly be a chance of joining if you've be 'trained', and not just if you have "the qualifications". But it seems you would have to be in the trade for some time before you can join.