Thanks for all these, I'm adding them to my bucket list.  I'm going to the Lake District for the first time in February, so I might try that drive (although I'm guessing that in Feb. the weather won't be good enough).

There's a glass platform at the top of the CN Tower in Toronto, which I sat on.  I practised by using the glass floor in the Spinnaker Tower in Portsmouth (I've danced salsa on that!).  I used to be terrified of the combination of glass and heights, but as I get older, I've become bolder.  The exhilaration makes it worth while.  That one in the Alps is really amazing. 

The one I'd really like to have the courage to do is El Caminito del Rey.  Have a look at around 3:00  :

https://www.youtube.com/watch?v=s8IrCKIiXd0