. . .What about a private observation pod on the London Eye at the top of its rotation at sunset? . . .

Not a bad idea since one could have champagne etc. if I'm not mistaken. It would indeed be a memorable moment in a pod all alone.

( though at my stage, if I did something like this with my wife as a reproposal, she'd probably tell me to go jump in a river, which of course would be uncomfortably too close for comfort).

good luck with whatever you choose.

Barry