Skoda Fabia 2002 - Security system playing up - tumeke

The system that reads the key and allows the car to start has been playing up. Sometimes the car starts, sometimes not. A warning light on the dash blinks indicating that the key is not recognised. Visits to 3 garages (and a hefty bill in one for replacement parts supposedly fixing the problem!) have led to nothing - the problem still exists.

Has anyone else had this problem and knows a solution? The only thing I can think of is to override the key recognition system - if it is possible. This security system is useless if even I can't use the car.

All help and suggestions joyfully received.