Road Wheels & Road Wheel Recommendations?

Riddle me this. I currently have 32h open pro rims on campagnolo centaur hubs like these; http://www.totalcycling.com/images/large/21003_134355.jpg
I've started entering closed circuit races, lasting around 1 hour. Will a wheel upgrade be the best use of my money? I have a budget of around £400, does anyone have any recommendations on a decent wheelset for racing?

Yes wheels would be the best use of your money. What kind of circuits? I would imagine that for crit racing (I only race track and tt's) that a low weight film would be useful and a hub with more engagements - easier to get back up to speed after breaking in corners etc. 'aero' wheels are often a bit heavier and don't spin up to speed that fast - though they do stay fast for less effort once you're there.