Definitely go for a white tux, everybody loves the "crazy edgey party animal" at formal events.
M&S don't do just cheap suits. They have a nice range of formal wear, too. Including dinner suits (i.e. DJs and dinner trousers) and some very nice dress shirts.
M and S, I bought a suit (jacket and trousers) a tie and a shirt for not much more than the rental. If it is only once or twice a year it makes sense. It also avoids going for a fitting, picking up and returning the suit. Just measure yourself and buy online
http://www.marksandspencer.com/Partywear-Suits-Mens/b/2306603031
That's not black tie though, black tie means DJ and Dinner trousers not just an off the peg suit.
Also, black tie = tuxedo / dinner jacket with bow tie. Only.
Not a waistcoat/cummberbund fan then?
Kilt and the trimmings is acceptable for black tie also, though only if you have a real connection to Scotland.

Kilt and the trimmings is acceptable for black tie also, though only if you have a real connection to Scotland.
