A while back I upgraded the wheels on my secteur from the Mavic CXP22 with Gators to Dura ace C24 with Michelin Krylions. The bike felt better, but the main difference was on longer rides. The reduced effort seemed to really help me out.
But that was going from "Not bad" wheels to "Ferkin lovely" wheels.
It seems that you would be going from "very nice" wheels to another set of "very nice" wheels. They would be nice, but Im not sure noticably nicer. I think as long as they seemed like they would be servicable for the forseeable future I would keep them.
If you have £300 burning a hole in your pocket, how about trying a proper bike fitting session... or treating yourself to a mainenance course and a toolkit and a bunch of flowers?
Paul
(The flowers are to distract the missus while you sneak the toolkit passed her)