I did this is as my first 600km ride last year. Climbing is only a real issue out of Chard and out of Bath - out of Bath on the second day was HARD but that wasn't helped by oven like temperatures and no shade. It is unlikely you will face such temps this year I hope for your sake - the weekend we did this was the same weekend those marines died of heat exhaustion in the Brecon beacons
If the heat is on, there is a lovely stop off shop in Bath you can use before descending that sold peaches sent straight from an express train from heaven - highly recommended
Participation was quite low as it was only a week or so before LEL, I hope it picks up this time around.
It is a really nice route, you will get to see so many lovely places, Salisbury was a highlight on the first day, the Cotswolds on the second, Bath is always nice (if at the bottom of a bottomless pit
).
You will enjoy, good luck