Over the past few months I have had very little hot water pressure in any of the taps and the shower. The water tends to come through as a trickle and often is just luke warm. The boiler appears to working OK, I have no leaking taps so can't find a reason for this happening??

Have you opened up a faucet and pulled the cartridge to check the hot water inlet ports? While you have the valve open turn on the hot water to flush out the supply.
Good luck, Tom