fitting a shower (water supply)

[delmel]

I have a downstairs loo which i potentially have the room to add a shower unit into. My question is regarding water supply.
The basin has a hot and cold feed (have to establish where the cold feeds from mains or tank will investigate tommorrow). Is it permitted to share the supply to the basin or does a shower require its independent water feeds ?. Prefer power shower

 

[TALU]

Not sure on building regs, but cant image why you should not.

If you have a heating storage tank not a combi, go for hot/cold supply with thermostat and an inline pump, so much better than the electric cold feed so called power showers.