I have a worcester bosch boiler, whose pressure dial is all over the
place. Sometimes it's at close to zero in the red zone, sometimes it's
just in the green zone.

It's been behaving this way for many months.

Is this a problem with worcester bosch boilers in particular, or
boilers in general? When we get a British Gas engineer to fix it, he
increases the pressure so it's in the green zone. After a few weeks
it's fallen again into the red zone.

The boiler is ten years old. Can it be fixed? Should I be looking at a
new boiler? Apart from the pressure dial, the boiler is fine.