Mav, thats one I havent heard - the lazer key thing - will tell Alan.
The last tank he bought had the same prob - but he phoned around first to find out costs for the replacement lock (not as expensive as he first thought) - and then drilled out the tumblers to get existing one out.
It's a different filler cap on the 749/999.... same as the Uglystrada...
There's effectively 2 holes, one for fuel and one for the locking mechanism, which has a plastic cover between the catch/lock and the fuel, I'm guessing if he's managed to get that off from the inside he should have access
The problem I see is the cover though will be blocking the lock from underneath, coupled with the fuel pump being right at the back of the tank, near the seat pad