In reply to SophieToast:
Depends on climbing and grade and budget.
Sub-HVS and in Britain:
Gower, possibly Cornwall.
HVS and upwards and in Britain: Cornwall, possibly Pembroke.
Europe-wise, anywhere in Northern Spain has great surfing and great climbing but you may have to drive between them i.e. the best climbing is not on the coast.
But, honestly, the hands-down winner for this question is the south-west tip of
Portugal. Amazing beaches, consistent surf even in summer, and good climbing, including a nice mix of trad, sport and DWS. September will be the best season, with warm water, probably good weather, and hopefully some early autumn swells. Sagres is a cool little town too. Though if you stay at the campsite, bring your ant-powder! :O