Britony Combi SE boiler lacking pressure?

I have a Britony combi SE which is lacking pressure. The needle reads as low as .5 bar sometimes and won't opperate indicating low water pressure. My neighbour also informed me that my overflow has been leeking/dripping. Are these two problems conected? and how do I go about fixing it? Also is it expensive. Many thanks

Dave Brayford
November 2007