I reckon if you looked hard you'd probably find something-ish along the lines you want in between Worthing and Littlehampton. Seaside, harbours 2 hours to Wiltshire, still on a direct link to London/Croydon and a starting-to-burgeon folk scene + plus most sunshine in the UK (which isn't saying much compared to Rio, but a start!!)

Happy hunting,

Hille