To return to trial lessons...
I was in a similar situation this time last year, I'd read the training and navigation books and was completely convinced I wanted a PPL and wasn't really sure I should bother with the trial lesson, since the first 'official' PPL lesson basically covers the same ground, only more thoroughly. I turned out to be right - I didn't enjoy the experience particularly because there was very little flying really (also because of a grumpy instructor who obviously wanted to be elsewhere) and didn't feel I really learned anything at all.
When I went on to the first lesson proper the difference was so astoundingly different. The briefing was in real depth, and very interesting, despite being similar to what I'd read. Throughout the flight the instructor (different one) drew it all together in a way that a book can't, explained everything and was really friendly.
Surely if you explain what kind of a student you're likely to be, the instructor (if not the club) will tailor it to your needs?