Ahem *walks into thread*..
Wellll
The Ernie Ball musicman Petrucci 7 string is a great guitar. It's quite expensive in comparison to the Ibanez models suggested but it also allows you more scope for customisability as you can choose from a huge range of colours, special inlays AND (the most important extra feature imo) you can have a piezo bridge installed if you wish, this is what may set this model apart from others. However the Petrucci models don't have floating bridges so if you're into heavy trem work they may not be for you, the Universe however..
The Ibanez Universe is also a fantastic guitar, although i wouldn't say the money extra you have to pay over something like an Ibanez 1570 is worth it, as all you're paying for is the DiMarzio Breed pickups (which are fantastic by the way) and the extra cosmetics. But if you want the real thing then you'll find a UV orgasmic.
You can also search ebay for an Ibanez RG2027 which is another 7 string prestige model with a fantastic flamed maple top, these are quite rare though but already come with DiMarzio pups as standard.
If it were my choice i'd go for the ErnieBall but that's only because at the moment i'm GASsing after a Piezo bridge and i've already got 2 Ibanez, one of them being a Vai signature model, the UV is still a fantastic guitar though.
EDIT:
By the way UV77s are easy to get in the UK, go to GAK for a start, if you search hard enough (well not
toohard) you can also find the Petrucci models, infact here you go:
http://www.firstguitarshop.co.uk/view_product.php?product=JOH32CTQ62
EDIT again!:
If you check the John Petrucci forums, in particular this thread:
http://www.petrucciforum.com/forums/showthread.php?t=33755 you'll find a guy with an awesome selection of Petrucci guitars, some 7s aswell, he's actually looking to sell some, he lives in Europe also, apparently he's a sound guy and keeps them all in fantastic condition, I don't know him though.