Round trip for one week - route wanted

I'm planning a round trip across the south-west of England. Does anyone have an idea for a fetching route? Start and fish Portsmouth, just few traffic, not too hilly (I ride a vintage Freddie Grubb fixed gear bike and I'm vintage too...) and with bicycle friendly B&Bs?

How about a cross channel affair?

http://en.tourdemanche.com/ . Ride down to Weymouth, over to St Malo and back up to Cherbourg.

Or a Caen loop:

http://bikeroutetoaster.com/BRTWebUI/Course/50103

Good idea. Thanks!

Along the to Newhaven, across to Dieppe on the ferry, along the french coast to Caen/Le Havre/wherever and back across? Would make it slightly flexible in that if you aren't feeling like you are going to make Dieppe to Caen you do Dieppe to Le Havre instead.

Google maps with cycling routes clicked gives these as a rough idea of miles.

Portsmouth -> Newhaven 60miles
Dieppe -> Cherbourg 175miles(if your feeling really fit)
Dieppe -> Caen 100miles
Dieppe -> Le Havre 65miles

Nah, stay in the UK. These are rough areas, going from 60- 70 miles per day
Day 1- Portsmouth to Illchester
Day2 Illchester to Lynmouth
Day 3 Lynmouth to Dawlish
Day 4 to Dawlish to Burton Bradstock
Day 5 Burton Bradstock to Sandbanks.
Day 6 Sandbanks to Portsmouth.
Total 350 miles so chuck in a 7th day and split the route down further and you've got 50miles/ day. Perfect tour.

Thanks for all suggestions! All are very helpful.