Fitting a programmable thermostat on a Vaillant Turbomax 824E?

I've got a Turbomax plus 824E which is working well for me - but the timer on it is from the stone ages and there is no thermostat in the house. I'd like to fit a programmable thermostat in the hallway and use that to control the boiler (on/off times and temperatures).

I've taken the front of the boiler down but have found that the timer that's fitted is custom to the boiler, and fits using some "spikes" on the back of the timer that push though some grips on the control board.

Does anyone know if it's possible to fit an external timer or room thermostat to these boilers? I've looked through the manuals and the vaillant site and all I can find is how to pay £70 for a digital 7 day timer (with no advance or 1 hr boost function :( ).

TIA, James.