To drop parachutists you need a BPA parachute pilots certificate. They normally use pilots who are also parachutists so its difficult to get a look in if you don't. They also tend to use type rated aircraft now and frequently hire them in with crews from Easter Europe. Towing gliders also seems to be the preserve of glider pilots with a PPL, very much a closed shop.
Ever thought of joining a RAF Volunteer Gliding School, they teach with no need for loads of expensive qualifications.