I know I have completed 45 events of 50K or more, along with two spectacular DNFs, but I'm afraid my training programme, such as it is, is not necessarily one to be emulated!
The main factors are:
learning to eat (normal food) while running
spending lots of money on different rucksacks, shoes, socks, and other kit until you find the ones that suit (if you ever do find them ...)
trying to look after your feet
lots and lots of fun and drama
As to training there are two general methods: very long single runs (max probably 35-40 miles), or back to back 'regular length' long runs building up to say a max of a 20 followed by a 30. I'm in the former camp with a longest single training run to date of 60 miles.
Yes, take that. Once you come down to the Thames early/late evening it is surprisingly cold and you might be glad of an extra layer then. You will certainly need one on the Downs. I hope your injury allows you to finish. You will probably know by Goring whether to carry on or not.
Very nice 14 miles and 3900' in the Brecon Beacons this afternoon: Fan Fawr 2408', Fan Frynych 2064', Craig Cerrig-gleisiad 2064', Y Gyrn 2031', Corn Du 2864'. Three of these are 'extras' not on the 10Peaks route.
I'm going to be attempting 19 peaks. There are only three others over 2000' in the central or western Beacons, but they are outliers and I would struggle to include them as well in 24 hours. One of them might be possible. See how this year goes.
I never tire of the wonderful, changing views to be had from each summit in turn, showing where you've been and where you've still got to go.
Best countryside in the UK in my opinion.
Often in the middle of nowhere scrabbling around in gullies and crossing bogs but nothing untoward.