For you, then you will have to take your chance and find out eventually what will be needed. Don’t be surprised if it is not only flying retraining already discussed, but also EASA examinations and flight test.
For your last query, again I don’t know for certain but if current and they have a BGA licence I believe that they could convert, They might find that easier if they were to join a BGA club at the time. They couldn’t reasonably expect the BGA to work for their conversion if they are not members of a BGA club. Their alternative AIUI would be to continue flying but only in Annex 2 gliders.
As for your last comment, you evidently have a biased and distorted view of those of us in the BGA. We do not think we have a monopoly, some of us have over the years been involved in helping non-BGA clubs to join but certainly we could not make them. I think I know a lot more about that than you are likely to, and certainly I know more than you give any credit for.
Chris N