Thanks both for your tips.

Unless I'm missing something, I think I'll pass on the MKS Gen L board. I really want to do the dual extruder upgrade asap as I want to start using PVA for the supports (I'm sick of trying to remove supports already, and I've only printed a few things). The touch screen doesn't appeal to me either - i prefer good old fashioned controls.

Looking round, I think a RAMPS 1.6 board would probably suit me best. Having a seperate Arduino board leaves more scope for hacking, and if either board packs up I've only got to replace one of them.

Regarding fire safety (a big concern I had for the original set up), do the RAMPS boards have decent MOSFETs built in? Is it worth me upgrading to 24volts? And if so, would it then be a simple case of switching power supplies or would I have to replace other parts?