Potterton Performa Boiler 30 HE No Pressure + internal leak + drain running?

Hi,

I have a Potteron Performa 30 HE that is now showing a few symptoms.

1. The current state of the boiler is that it will not light, with the error light suggesting that the pressure is too low, which makes sense with the following further details.
2. When the system is re-pressurised (by letting in more water), water starts to flow straight out of the drain and runs outside, just as fast as it's let in.
3. Furthermore, water is pouring from inside the boiler. By removing the cover, it looks to be coming from the top and running down the centre and left hand side.
4. The boiler has been losing pressure slowly for quite a while and has needed topping up every few months. However, it has become more frequent recently until it won't fill up at all.
5. I have sometimes heard the drain from the boiler trickling with water . Similar to now but on a less scale. I 'think' it was worse with cooler weather.
6. The inlet valve that I have been using to top up the pressure has always been difficult to turn off fully and the hose has never been disconnected. It may be possible that water has been seeping in to the system. Saying that, I have never noticed the pressure too high.

This happened a few days ago though I managed to get some pressure to stay in the system. However, today I cannot get any pressure in to the system and it seems to come out (from inside the boiler and through the drain) just as fast as it's replaced.

Can anyone suggest what could be causing this?

Many thanks,
Adam