This is a poplar question on here , personally I always point people in the direction of a plumbers merchants , stay off the internet unless you are buying a recognised brand who sells through a merchant .
Ask your plumber for their advice too. As people who fit day in day out they will 'know' what is good VFM.
Cheap is ALWAYS rubbish and is often difficult to fit, you WILL pay an ultimate price.
Superb quality vs price is Roca in my experience.