I've never ridden the official Fred Whitten but have done all the big climbs and have ridden a lot in the Lake District over the years. I've got over the worst of them (wrynose/hardknott/kirkstone) with a 39 inner ring and a 27 on the back though as @skinny suggests I would advise going for a 34 or 36 at the front and a 29/30 at the back to make it a bit easier on your legs. Check your brakes are set up properly as a lot of the descents have sharp corners and are very steep in places - the roads aren't like true mountain descents where you can just open up. You'll want to build endurance and make sure that you're comfortable on the bike riding for four+ hours. I'd say ride outdoors a lot if you can - as in get used to riding in crap weather. It can turn really nasty in the lakes and I have previously been caught in a very grim snowstorm whilst descending hardknott which was awful. It seems to rain there non-stop. Being comfortable in crap weather and not getting demoralised will probably be just as valuable as being able to smash out the kms
I've never ridden the official Fred Whitten but have done all the big climbs and have ridden a lot in the Lake District over the years. I've got over the worst of them (wrynose/hardknott/kirkstone) with a 39 inner ring and a 27 on the back though as @skinny suggests I would advise going for a 34 or 36 at the front and a 29/30 at the back to make it a bit easier on your legs. Check your brakes are set up properly as a lot of the descents have sharp corners and are very steep in places - the roads aren't like true mountain descents where you can just open up. You'll want to build endurance and make sure that you're comfortable on the bike riding for four+ hours. I'd say ride outdoors a lot if you can - as in get used to riding in crap weather. It can turn really nasty in the lakes and I have previously been caught in a very grim snowstorm whilst descending hardknott which was awful. It seems to rain there non-stop. Being comfortable in crap weather and not getting demoralised will probably be just as valuable as being able to smash out the kms