Alas, the old fob was thrown in the bin, and as luck would have it, the bins were emptied the next morning
"Keys cut from a photograph of the blade can be had". very interesting, has anyone got more info on this? Sounds doubtful to me, but happy to be proved wrong!
I will follow up on the comment about Timpsons having a machine that can clone the transponder, that sounds like a good way to go. Failing which, looks like I will need to buy a transponderand visit someone with a T4/ability to program a new key. Or just live with one key...