the south. wild. you'll be lucky until you get to the vicinity of dartmoor.
a few off the top of me head
if you want a longish walk with around 900m of ascent then a circular around lewes in sussex is a good one. you can make this as long or as short as you like using southease station.
1 - head out of lewes up to the golf club then across a bumpy bit to glynde. from glynde head due south and up onto the south downs way (the aerials guide you). follow the sdw along and down to southease (where you can get a train back or walk aside the river back to lewes.
continue to follow the sdw up and coninue upon it until you reach mount harry (at the northern edge of the escarpment) where you turn right and head back to lewes. en route you may choose a shorter way back via kingston.
i think clockwise is the best way to do this overall.
2 - from southease eastwards along the sdw down to exceat is a very pleasant walk. (if the wind is from the north you can watch the paragliders) bus back to eastbourne/brighton/seaford
3 - the last section of the vanguard way from berwick to seaford is an excellent and picturesque walk.
4 - the seven sisters from exceat to eastbourne along the sdw
5 - from wye to dover on the north downs way is a cracker too - especially the approaches to Folkestone.
6-Kent sections of the Greensand Way are nice
7 - from holmwood station to dorking station going up to leith hill (highest point in south east england) and the head north to the north downs way and follow that to dorking. if you're feeling athletic you can take in box hill, down through juniper bottom and up the other side to mickleham and continue north to leatherhead.
it may not be wild about these parts but it' scertainly quiet. on a week day you'll be lucky to meet anyone and on weekends once away from car parks or the "honey" routes (e.g. sdw) you'll have little or no company aside from dog walkers.
the chilterns have some very nice walks indeed and that area seems to have more paths than you'd think possible so a 25k map is essential. station to station is very do-able.