Carl, I know you are in the middle of lejog but perhaps try and do some long sustained efforts too. At least 50km and perhaps with a nasty climb thrown in too so you make from sustained effort into something that taxes you aerobically. You will need to fuel for them but they are hugely important in building stamina and enabling you to build on your power. I did this 2-3 times per week in the autumn with a nice 30w plus jump in ftp with 3 kilo weight loss.
Zsun 2 hours will be more than enough to start with, then WBR 60miles followed by WBR 100miles
