Anyway, first of all I'm only going to be buying the older games, they are pretty cheap. I'm unsure of how much i would actually pay for a game, but theres lots of the old ones that I can get and then we will see..maybe one or two expensive ones per year.
You're going through the same process most Neo Fans go through. Almost everyone buys an AES first unless they buy a cabinet. Consolized MVS boards seem prohibitively expensive at first, and almost everyone gets into Neo Geo because of the older games, like Samurai Shodown 2, which is really common and inexpensive on the home system. A home system looks nicer and seems like the right choice, but you'll almost certainly change your mind later.
Then, it won't be long before you want to play the Metal Slugs: part 1 is the best...and also the most counterfeited cart for the system. If you even consider buying that cart (assuming you have $1000-2000) make sure you're an expert on detecting a fake. And it's inevitable that the newer games will start to look appealing: if you're into fighters you'll want to play some of the newer ones like MOTW and the Last Blade series; and if you're into shooters you'll probably want to play Pulstar, Blazing Star, and Twinklestar Sprites (all kinds of stars!). Eventually you might find yourself wanting an MVS exclusive, like the incredibly fun Shock Troopers.
You'll consider buying an MVS->AES converter like the Super Converter II. If you do, you'll be ok with it at first...until you start to notice the scaling issues. And then Metal Slug X won't play because you have a revision 3-6 motherboard. Or maybe you'll end up with a Phantom 1 that will abuse your cart slot and won't play the newer Playmore games.
OH, and the UNIBIOS (
http://unibios.free.fr/ ): want to be able to change the region of your games, use cheat codes, soft reboot, insert coins from the joystick, or play the games music in a sound test mode? I hope you're good with a soldering iron, because the AES' BIOS is not socketed, so it will be a real pain to swap in, even if you have some experience with that sort of thing.
Not to dash down your excitement, though. I love the home carts, and I'm not at all saying that you made a bad decision in buying an AES. Alls I'm sayin' is: an MVS is a nice supplement.
Since you're in the UK, and probably looking to build your collection, try this thread out for some home carts:
http://www.neo-geo.com/forums/showthread.php?t=180422
