I'm in Milton Keynes.
On the JAMMA cabinet issue I will soon have a cabinet I gave to my father inlaw for all the grandchildren to play on coming back as he is moving away to the IoW.
Its just about the most mameable cab I have seen. Its an Apollo JAMMA cabinet in reasonable shape

and isn't the prettiest cab I've seen but it has all access from the front, rotatable monitor (and I mean properly rotatable - you dont have to unbolt it or anything you just open the front and turn the monitor), scan coil switches at the front, video controls at the front (I think) , fairly flat control panel and I think its fairly deep so reasonable space for a two player setup. It also seperates into a top and bottom half so can be much easier to transport or get upstairs.
If you can live with the looks then it would be great for mame. If anyone wants to email me contact details I'll let you know when I have it back at my place and up on ebay.
If your in a rush then probably the best place to look for JAMMA cabs could be here.. If anyone has/knows of cheap ones then we in there do
http://games.groups.yahoo.com/group/ukvac/I think that part of the problem is that anyone that has a supply of decent JAMMA cabs is maming them themselves and siting/selling them

Cheers
Andy