Thank you, both!
I did look up Wycombe Airpark but note that it is an all-grass airfield. I've got some names of places at Elstree and Denham that I'll get in touch with over the weekend, though.
RE Fairoaks - this looks like an ideal place but I have only been able to find one outfit there - Fairoaks Flight Centre - and they do seem extremely expensive. I don't know if it's something I will need to get used to living here, but £200/hr for a PA28 is a big jump from the £130/£140 I'd pay at EGGP (which I'd have thought is a much more expensive base)! Does anyone know of any alternatives?