Good deal ?

I would say go for it, it says make offer so hit him at $125 or roughly £70 and stress the fact that you don't NEED it but want the parts for extras/spares ! That's not just a head he's got thats the cylinder and it appears to be in good shape. Just the cylinder, flywheel and that case alone are well worth $125 ( don't know exactly what that would translate to in your money ). If the brake parts are hydros than that would be a great deal even for his asking price.

if the cylinder I in good shape id do it