Rules... high speed goalposts are making aviation quite hard to follow.
Some gliding CFI's have been authorising tug pilots for many years... but they are no longer able to do so under new rules.
So, I have to get a glider pilot licence, at least 100 hours P1 for insurance purposes, and taildragger time for the Pawnee.
My first solo flight 40 years ago was on a Rollason Condor, no flaps, G-ATAU
The new rules are deferred until April 2018 - in the meantime you and gliding clubs can choose whether to continue the way it was or to adopt EASA rules. There are a load of CAA derrogations that give details. Insurance - well that's another matter. In summary you don't NEED a towing rating at present. Your club's CFI or nominated deputy (i.e. usually the Chief Tug Pilot) can train you and let you loose when you reach the required standard.
Some 7-day a week clubs are more interested in weekday tuggies with limited gliding because they sometimes have difficulties filling their weekday rosters. Weekends it is a different matter with plenty of aeroplane pilots with gliding experience.
Having trained tug pilots with and without prior gliding experience my experience is that most power pilots can adapt to the different environment easily if properly briefed etc., whilst some just don't have the aptitude.