Re:
Did a 350 mile round trip from Skipton to Milton Keynes + 500 to Cardiff, both for Marins, both for my mate and both years ago in the early Retrobike days.
I've done plenty of 200+ trips to Derby, Nottingham, Anglesey (earlier this year for my gravel bike), Middlesbrough, Darlington, Ambleside etc, etc. It would have to be something really special to commit to much further these days though.