It’s a generalisation, but there’s a good surf scene around Bournemouth and further west, lots of windy water sports around Poole and further east. Surf’s more consistent in winter so you’ll need a winter wetsuit, boots, glove and hood to get the most from it, but I was surfing yesterday in a 1mm neoprene rashvest and board shorts.
The island is pretty decent for all of the above water sports, but suffers from employment woes unless you’re public sector, tourism, marine or aerospace (as a rule of thumb). There’s obviously also the ferry, which is both a blessing and a curse. It’s also a ghetto, apparently.
Lots of tech and creative in Brighton if memory serves, but a cost of living to go with it.
South Downs stretch from Lewes to Winchester, and are easily accessible from the coast from Brighton to Portsmouth. There’s obviously QECP near Pompey too. However, it is chalk-based – get your non-slip tyres out for the winter!
New Forest is flat-ish and full on NIMBYs, but the riding round Bournemouth is meant to be halfway decent (and drains well). Swinley is also not too far in the car, so all-weather riding is available. Tidworth and a few other DH-orientated spots are dotted around too.