140km loop which is the Shipwrights Way from Bentley nr Farnham to QECP – SDW to Winchester and Oxdrove / Bridleways / Basingstoke Canal/lanes back to start is a nice day ride ideal for a CX bike. Shipwrights Way isn’t yet signposted from Borden to Liss so you need to work-out a route.
From Guildford you can ride the Downslink to the coast or pick up the SDW in either direction – I combined this with the above to Winchester to create a 225km loop.
I’m training for a SDW double so will be riding to Eastbourne and back this weekend!
Further away, Braunton 150 is a recently established loop around Exmoor.
Also check out the Bearbones forum.