Glider towing positions are normally only open to holder's of silver 'C' gliding qualifications, there are occassional parachute droping opportunities.
The other option is banner towing, although there are only a few that do this in the UK. However, can I stress that banner towing is potentially very hazardous, particularly for an in experenced pilot and you have to fly very accurately for the pick up and be comfortable with slow flight.