I think I would agree re the training required through summer for an autumn race. I play a lot of golf and dont really like running in the heat so it is all a bit difficult and I feel I have been really having to fit everything in for the last 3 months or so.
First 18 miler today which went well up until 12.5 when I felt a pain in my hamstring and had to walk the last 5.5m home. 3:30 is a long time without any water - I was anticiapting about 2:45 time on my feet.
York 10K next weekend looks in doubt now but I don't think a few rest days will harm anyway as I was starting to feel a bit fed up with the continual training and battle to fit everything in.
Looking at the overall gain at York of 75m then it is not as hard as London which has 132M (best evidence I can find). London is supposed to be pretty flat and I doubt York will be harder in terms of hills.
Motivationally it will be much harder with long sections that have no support, hopefully they wil be broken up by drinks stations.