Well, I followed those links you recommended guys and "Meetup" is really interesting, I've joined that group and will use it for other activities than tennis. Racket Friends might come up trumps for me also. In my search for finding tennis partners, I came across another site that connects people who want to find partners for many activities including tennis.
Their aim is to "connect people who have similar interests in wholesome leisure activities". They have three leisure activities: Recreational Sports, Outdoors, Fitness & Wellness. It's a huge site so here's the link to their tennis section:
Leisure Clique Tennis Partners - they have some useful discussions on tennis skills. I found a thread on breathing techniques very useful, it's not an aspect of the game that I'd really thought about. I tend to gasp in a lungful of air and hope it'll last out the rally!
I've joined them. I'll let you know how it pans out for me.