pressure drop also dripping from the overflow?

Hello I purchased a Sabre 24 almost three years ago and I haven't had any problems with it till recently.At the begining of December I started to notice the boiler was losing a little pressure over a couple of days . I didn't really find it a problem as I would adjust the pressure manually.But recently It has started to lose a lot of pressure and requires myself to top up the pressure almost every few hours and at the same time my neighbour who lives below has mentioned that the over flow which exits the boiler through the wall has started to drip profusely. Does anyone have an idea what the problem could be.