As a PPL, you may stuggle to do this. Lots of people have thought of this as a good way to build hours for free, sadly, it doesn't work out like that most of the time. Several friends have enquired at various places around the country and the reply is fairly standard, they want a pretty experienced PPL (usually with taildragger time as well) and they often want you to be a glider pilot (to 'Silver' level, whatever that entails) already and be able to devote quite alot of time to the club. I'd say it's quite a sought after gig ('Free' flying always will be, let's be honest).
They only person I know who does glider towing is already an experienced CPL (despite being very young) and has had connections with his club for years (he's also a qualified & current glider pilot), additionally he's an extremely talented and safe pilot.
Give it a go by all means, I wish you well and hope that my 3rd party experiences aren't repeated everywhere.