Hi
Go to plumbers merchants and buy a syncron motor (£10 or less) Turn the power off to CH system and loosen the small cross head screw at the end of the silver cover.The silver cover will then pull off. Inside you will find a motor the same as the one you have bought. There will be 2 wires from the motor which will have connectors (Normally twist togeather type) Undo the two connectors and seperate the wires. On the new motor you will see 2 screw holes, one either side at its base. Locate the same screw holes on the old motor and remove the small screws, taking care not to loose them. Once removed the old motor will then pull free. Replace with the new motor ensuring that the small drive gear engages with the cog and replace screws. Re-connent the wires, it doesn't matter which way round and the replace the cover and tighten the securing screw.
Turn power back on and test by turning the programmer on to CH then HW then both and observe the small lever that sticks out the end mooving.
Have a cup of tea you have earned it, hope this helps any problems, let me know.
Steve