I don't know about in the U.K. but Iwould asume you can get what is known as a multi-tap ballast for your fixture just like here in the states. It allows you to run your light at a higher voltage witch will use less amps and cut down on your cost alot. Hope this helps you a little. What ever you do don't try to save money by switching to fluro's. First of all you won't like the results and if you figure that you need 10 40 watt fluro's to equal 1 400 watt hps the light to power ratio sucks. PEACE