i recently changed my bathroom suite using the existing pipe feeds using compression joints and plastic connectors but now my new mixer taps have less water pressure in the bath and basin, taking ages for bath to fill, any sugestions.
That happened to me, also. It's not pressure that's the issue, but flow. It's most likely the design of the taps that has reduced your flow. But, apart from swap the taps, I've no suggestions.
Agreed. The new taps require more pressure to give the same flowrate as your previous ones. You could try taking out any fancy device screwed into the tap that creates efforvescence in the emerging water (if there is one). That may increase the flow.