Having pondered, I rang wilson's (dealer) back after the post above, and after 25 minutes of telling them their price must be wrong, it can't be FOUR times as much, they said oh yes sorry we quoted you for a compressor, it's ONLY £723 to replace, oh and plus the £120 to diagnose of course. Bargain. Really not impressed, the experts being told they're wrong by a novice customer. Waiting for their service manager to call back, three days on the trot now, nothing so far. What happened to good customer service? Grumble grumble etc