Don't get the Dalkiia wheels Stu. The bloke in GBs (Scottish ex-pro with the very dry sense of humour, prefers to have a chat with you to actually serving people
) said they were crap. He said that because they were clinchers not tubs, and with such a deep rim, it took four of them to wrestle the tyres on. He also said the build quality was pretty poor. To paraphrase him "if you want to pose fine, otherwise don't touch them."
If you want deep rims then the Planet X are probably best bet in that price, although if you're hammering around Surrey's pot holed roads in SL & SERRL races then I don't know how long they'd last, good for TTs though.
Campag Euros would be good, and strong and a logical step up from your Zondas, or you could go for Campag Nuetrons. Great wheels, good for climbing, and light so accelerate quickly.
I'm sure you know I'm not a powertap man but ignoring my prejudice I'd make sure you'd definitely use it to train and get any proper benefit from it. If you're not going to use it to it's max and just have a lot of graphs and some nice numbers then you'd get much more VFM from wheels, which you certainly will use. Powertaps may be the new must have toy in the club but you still kick their arses each week without one.
Please, not another bloody powertap!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!