Update: I fitted a 15mm full bore isolator to improve the flow but unfortuntely still no good. Its got me thinking that perhaps I need to replace the mixer tap with a conventional type one with a spout that points downwards, rather than a wide spout that shoots out sideways (see Sean's pics above). This way the hot water should drop out of the tap?

Also quick question on basin waste, bought a plughole etc (one of those coin flip type ones). However its leaking!! I've fully sealed it etc. Now it does have the overflow holes around the sides but got a feeling I may need one without the holes? How do I know if my ceramic basin has built in overflow?!! (sorry im new to this plumbing lark and the old man is on holiday at the mo!!)

Chris