if you do it, take your time. my girlfriend was riding up to about 5/6months when it started getting too difficult. that was just local stuff and commuting, i think the last big ride was about 3 months in, which included part of the C2C route to newcastle as we live by it. hills were the most problematic, which there are a few of on the C2C in the lakes/western pennines
i take it you doing the sustrans C2C route btw? if you are doing it with a support vehicle maybe you could do the odd flatter day and get lifts for the hilly days
oh and congrats on the news 🙂