[getting back on topic . . .]
Student1470,
Your Air Cadet experience will be very useful, once you've shaken off any rust. The BGA system relies on demonstrated competence rather than licences, and all of the ATC cadets I've flown with have been very competent, well trained pilots.
There will be extra training on stall/spin avoidance & recovery to do and circuit planning the civvy way is slightly different. Other than that you will find it all very familiar and shouldn't take long to fly solo again.
Rufforth's K13 will be quite different from the Grob, Sutton Bank's K21 is very similar to the Grob. Sutton Bank also benefits from a soarable ridge.
Passenger carrying is a little more complicated. Past history suggests that two club members in one aircraft can get into twice as much trouble as a solo pilot; flying with a non-flying passenger (even if a family member) involves an additional responsibility. For these reasons, clubs usually require a little more experience before allowing pilots to carry passengers. Nothing too draconian, something like Bronze badge and/or around 50 hours total airtime.
Blink182,
Silver C is an accomplishment and lasts forever. At the moment you need only satisfy an instructor that you are safe enough to let loose in the club's aircraft to be allowed to fly solo.
No-one knows what the transition requirements to EASA's Glider Pilot's licence will be, but a random guess would be equivalent to the BGA's 'Glider Pilot Licence'. Bronze badge + XC endorsement + 5 hours P1 in gliders in the previous 12 months required.