So whilst The Shark went in to have an intermittent speaker cut out investigated, I also asked the electronics chap to check out my second key, specifically the remote part. The key's remote central locking has not been working for a while (replaced battery), and my primary key is fully functional. Anyway, after having a look at it he advised that the remote is still emitting a signal when you push the buttons, it's just not the one the car is expecting. Something like...
When you lock/unlock via remote, to prevent some enterprising thief from picking up your "signal" and then playing it back to your car and unlocking it, they rotate through (presumably a fixed) cycle of "handshakes". Therefore, only the remote and the car know what the next handshake is going to be. Apparently my second key has "forgotten" which handshake the car is expecting and the car refuses to play ball.
Now the questions:
1) does this all sound plausibly non-BS?
2) do I have any alternative than a trip to the stealer to get this resolved?
3) anyone else battled with this?
As always, thanks for any help.