don`t worry i`ve been doing this for years carrying to much weight but having enough power to get me up the mountains,7 years at majorca training camps plus over stuff.this year maybe a once in a life time thing and i don`t want to spend two weeks with my heart rate in the 180`s so i`m making more effort with the weight, 30 miles a day is easy distance wise plus we do a 60 mile club run on sunday mornings if i can get up.i could do more miles but i do my miles riding to work and back so there is only so much risk you want to take with idiot car drivers(not supra owners)i have a 100 mile route i do which has loads of hills which i`ll do soon but i`m riding a fixed wheel at the moment 48/17 which is great fun and good for power.
ratio for france should be 53/39 with a 12/27 on my bianchi or i have my eye on a bianchi with a compact on ebay.
have you done the gnr as i told it`s harder then the london run.