hello cyclists! - I appear to have accidently entered a charity sportive from sheffield of 100miles!

so far I have done some rides round the peak up to 4 hours (45miles, 5000) as a peak - averaging 30-35 miles long ride once a week (3000feet approx, 12-14mph).

i also ride 35minutes commute 4/5 work days.

i was guessing build up to 60-70miles long ride??

throw in a longer evening ride (or 2) now its lighter??

any tips on fitting cycling and running together?

i have been doing long ride saturday, then long steady run sunday.

thanks.