You can't beat the coastal route from Poole Harbour, quick spin round Corfe Castle, then along past Lulworth Cove, Durdle Door to Weymouth and Portland. Compton Abbas is a great airfield, catch a glimpse of the nearby Cerne Giant (chalk hill figure) then back to the coast via Abbotsbury and on to Lyme Regis and thence to Torquay. Danger areas all along the Dorset coast, but pretty much closed weekends and holidays; London will advise.
Enjoy.
TMC