Just to wrap up that off-topic bit above about EKA codes, the Disco seems to have got used to my thumb on the fob button, and has been behaving itself for the past 3-4 days. Thanks for all suggestions.
Graeme,
Best guess would be the battery in the remote is getting weak so signal levels drop and its more prone to interferance.
Other issue with these remotes is the buttons on teh board tend to break away from the underlying track on the circuit board.
Replacements buttons are available on ebay etc and can be fitted with good eyesight and surface mount soldering equipment.
These days I just get my kids to do them as my eyesight isn't quite good enough.
Spare keys can be programmed to the vehicle using hawkeye or similar diagnostic tool.
B Rgds
Simon