In reply to Roobag:
Your profile says you're in Essex and some of the suggestions are a long way North in Scotland - makes me wonder if Ireland might be a viable alternative..
I did Gaelforce West last year (link:
http://gaelforceevents.com/en/gaelforce-west-info ) and it was fantastic - very friendly event in a beautiful location (and Westport is a delightful little town). No swim required, the 'aquatic' bit is a short paddle across the fjord on a sit-on-top kayak. The cycle section is largely on-road though, with a few miles of forest fire road a tiny bit of proper off-road and just the one rough rocky descent.
I'm not at all sure if it's the kind of thing that might interest you, but if it does I wouldn't hesitate to recommend it. There seem to be a fair few other events like it dotted about Ireland. Seems a bit odd that there seems to be nothing similar in England, I'd have thought there'd be a fair bit of interest in a Peak or a Lakes equivalent.
There was a drone buzzing about at odd times last year, got some really nice footage. I'm in it for about a nanosecond -
(Don't be fooled though, I think you only get a 50/50 chance of seeing the extraordinary view from the top of the mountain at any given time. The rest of the time it has a cloud sat on the summit like an over affectionate wet dog.)