Lee I assume that you've looked at Panshanger seeing as you are in Welwyn. There seemed to be a decent enough club atmosphere on the few times I've been there.
As BEgle says, why not get the microlight rating first (I don't know if they do this at Panshanger though). Some modern microlights are very capable machines and a damn sight cheaper than a SEP to operate in a lot of cases. Of course, if you are renting then this is irrelevant.
Another possibility is to buy your own PFA type aeroplane (Jodel, Taylorcraft, Condor, Luscombe etc) and get an instructor to teach you on that. It needn't be that expensive in the long term as you retain the capital asset of the aeroplane and "only" pay the running costs during your PPL.
I'm based at Rush Green near Hitchin, you are welcome to come for a whizz about in my Auster if you fancy a go in an old aeroplane. PM me and we can arrange something for when I get home in September.