Boiler firing up when programmer says off, and themo down?

Hey,

My programmer (potterton) has been set for my hot water and heating to come on for a few hours each morning and evening. But my (potterton) boiler seems to be ignoring my programmers times and firing up both on the hot water and central heating non stop. It isnt always firing, the bolier comes on and goes off, almost randomly it seems, but ignoring the programmed times.

The programmers red LED lights come on and it makes a click noise at the exact right times.

The only way to stop the boiler is to switch of the bolier plug.

Recently had the thermostat replaced and keep this low to try to keep the boiler off but unless its on zilch, the bolier still comes on at unwanted times.

There is a thermo on the boiler which is also down as low as it can be to allow the boiler to come on at least at the requested times (any lower and it doesnt come on at all)

It just seems that the three aren't listening to each other.

Any ideas? thanks Lauren