Forget it. These things sell for about that with a faulty motherboards. Like my uncle's but I don't think he has it anymore. Your best bet is to upgrade the 1200. I'm thinking of retiring my 1200D and putting all the stuff in the 1200T I bought.
But like I said, why not put a wanted AD in the free ads and see who calls? That's how I got my stuff cheap, plus nobody else did that in my area so the Amiga market was all to myself, no competition. Just make sure your polite and positive over the phone and ask how much they would be looking for. Just hope they say "Well I'm just hoping to just get rid of it" (*JACKPOT* lol). Although I couldn't leave a guy who gave me 2 500's, 1 600 and several bits and pieces for nothing so I gave him £10 for his time. :-) It's good fun if you can get the transport.
