All sorted. I managed to haggle the locksmith down to £60 for doing the driver's door (rather than the boot). Then I somehow disabled the alarm by disconnecting it and reconnecting it when the siren sounded with the battery disconnected :nerd: . Then I hopped into the back, opened the arm rest and found to my slight horror that they was a panel on the back of the ski sack. However, I dismantled the frame around the sack to expose a spring and latch mechanism at the top of the aperture. I jiggled that around and the back flopped down. Cut a slit in the sack to get my arm in and eventually found the key, thank God.
All in all could have been much worse.
Morals of this story:
- always put your keys in your back pocket when loading the boot,
- get a spare cut (the locksmith said he could do this)
- don't rush into the first expensive option
Thanks all for your input. :clap: