Hi Jowwy,
Though there are many a more experienced person on this site to advise you I'll drop my little bit of wisdom your way

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Personally I'd leave the Aksiums alone as I've gone through a shops entire stock looking for a pair with a decent rim joint and all of them where crap!
Fulcrum 5's are a great wheel and can be found in your budget range, Shimano wise I'd go for the rs20's they are lighter than the rs30's and better than the rs10's and can be had for £123 online from a very reputable dealer that sounds like rubble
What do I run? I've got a set of Giant PSL1's after the standard rear wheel on my Forme Reflex locked up at speed and destroyed itself. The PSL1 is a great wheelset if you can get it cheaply (retail at over £220 I think). If you have a Giant LBS near you see if anyone has bought a bike with PSL1's and then upgraded leaving the originals in the shop as you should be able to get them for a bargain? Just and idea.
Given that you seem to want to stay at the lower end of the budget though, give the RS20's a go?
It's not all about the weight of the wheel but "where" that weight is? Hub or Rim ? what bearings it's running on etc.
I suppose the most important part to think about is how cool they look
