+1 for the 5:2 diet. All Hail Michael Moseley ! It works, it really does.
But as to the OP and his doubts about L2B, you’ve got until next year, sir ! Loadsatime. So you can have a good snigger at myself who has until .. umm, this coming Saturday to ‘train’ for L2B. Saturday ? Well, that is because I am entered for the L2B Night Ride
. Similar route and effort but without the suntan. Full moon though
. And the longest ride I have done this year, what with one thing and another, is a mere 31
miles; last night (in the dark) in fact. I admit I have left it a bit late. Oh yes. So I am probably not the best advisor for training; I fully recognise that.
As to congestion, check out some of the YouTube videos on L2B. A revelation. At least the Night Ride is limited to 5,000 participants. The daytime one is 30,000 IIRC