ah – my favorite ride :wink: the first couple of days in the lakes are the hardest, be prepared to carry bikes for an hour or so up black sail. its a bitch but the descent to wasdale is worth it :) once over black sail, everything is ridable or at worst you can actually push a bike up it!
yorkshire dales and north york moors are much easier going, good opportunities to bag some big miles days as only doing 20-30 miles in a day on a 200+ mile trip is a bit of a downer on the first couple of days in the lakes.
orange 5 would be perfect bike – maybe less so if you’re carrying your gear as you can fit more stuff in a frame bag on a hardtail. if you’re supported then it’ll be fine for the job
first time i did it i was about average fitness for a mtb’er and did it in 3 1/2 days on my own carrying my own camping gear, mainly as i only had that time to do it! i’d say 5 days would be fine for an average rider without going crazy and 6 would be very comfortable
as for training you’ll be best upping your mileage tbh, maybe get up an hour earlier and make a longer commute to work, or just extend rides at weekends if time allows. you’ll want to stock up on energy food as well to see what you like/don’t agree with for long days out so its not a steep learning curve out on the trip