Tapping noise

When I turn the taps on in my Warwick xl I get a tapping noise coming from the floor area

An introductory post in the new members section would be polite, the WXL is a van conversion not a coachbuilt so not many WXL owners may read your post.

You do not state if there is water 8n your system, is it hot or cold water taps that cause the knocking, are you getting water out if the taps, more information is needed to provide any sort of helpful response

There is both hot and cold water on. There is water coming from the taps. When you close the taps the noise stops 
All the taps are the same.

Sounds like it could be the normal, on/off of the pump as the pressure fluctuates during water flow.

Does the noise vary with the flow, i.e. as the flow rate increases / decreases?

No the noise stays constant and doesn’t decrease over time.

As Spospe has said it could be the water pump pulsing on and off which it shouldn't do if the tap is fully open and there are no blockages in the system.  If this is happening it suggests the pressure switch needs adjustment.  No advice can be given on this until the type of pump is known.  If it's a diaphragm pump it could simply be a transmission of vibrations down the pipe or the pump itself vibrating against something.