I have two Deore 9speed mechs, one is 85mm between jocky wheel bolts and the other is 100mm. Both are in good working order, How about £15 posted for one or £20 posted for the two?
If your just experimenting I have a XT Rapid Rise which I crashed and then straightened but it never really indexed properly after that. You can have it for Karma postage only, [guessing about £7 or £8 pound].