Thanks to both of you! Yeah, it has been strange moving from being reasonably competent at one instrument (I haven't played in several years) to being a total novice at another. It's definitely helped me in some respects as you say V, but I have just ended up confusing myself with other things! It's a constant reminder of what I can't do yet, hah.
I'm not really looking into classical guitar no, especially since what I bought was an Epiphone Dot :)! Basically I want to be able to write songs, and the piano has always been a performance instrument for me, not something I feel like I could write on. I only really know classical music theory. Ask me about Scriabin, fine, ask me about twelve bar blues, no idea. Like I say, I'm into my Madchester and Britpop etc (though I like all kinds of rock), so this is a far more natural choice! I wish I'd picked it up years ago, so far I'm really in love with it. I'm also looking forward to being able to play with other people, again not something I could really do before.
I was definitely looking for individual lessons rather than groups, thankfully £25/hour is about what I'd reckoned. Maybe I will go over the basics myself and then look for a teacher? That book looks very handy, reminds me of the old Michael Aaron piano books.