I replaced some similar wheels on my old Allez with Open sport rims on 105 hubs, cost a bit more than £150 though. While a fairly basic wheel they were much better for general riding since they were a bit more flexible in the uppy-downy direction and a bit stiffer in the lefty-righty sense (the Alex rims were a sort of shallow V-section and the Mavics have a flatter sort of profile, plus more spokes). I found they made a great difference in general feel and comfort, but there was probably little difference in performance.
Still got those wheels, put them on my 'cross bike.
Spa Cycles is worth a look for budget handbuilts.