Brighton is one of the biggest tourist towns in the Country, so there's always lots to do, even out of season.
Firstly, assuming most people reading this do Tai Chi or Bagua or Chi Gung, there are a few good place to go and practice outdoors (weather permitting), namely
The sea front isn't so good to practice on generally, as it's either really busy or really windy, but can be very nice in the Summer.
There are a ton of alternative therapies and practices in Brighton too - probably easiest to look for these on the web, but chances are that you'll be able to find kindred spirits for whatever you practice somewhere in the town.
There are three main cinemas in Brighton, though one of these is some way out of town (at the Marina, a few miles east of the centre). The main cinema in the middle of town is the Odean, which shows most of the current blockbusters and the like. However up along the London Road is the Duke of Yorks, which is Brightons main art-house cinema, which shows whatever they decide to show and is comfy.
There is also a theatre and a few larger cabaret/comedy/music venues (the Komedia in the North Laine being the biggest) if you're up for something.
Most of the smaller music venues are also the pubs and clubs, of which there are many. For listings you could go to http://whatson.brighton.co.uk/ (non-music listings on that site are a bit patchy though), and there will always be something going on somewhere.
There's also a ton of pubs about the town, from trendy bars to shady local drinking joints. The Hop Poles along Middle Street is a nice friendly one (does good food too) but there are many others. All pubs are non-smoking now too, so if you smoke you'll have to join the crowds puffing away in the open-air outside.
The third cinema sits out in the Marina, which is also home of the city's ten-pin bowling lanes and private yacht owners. Out to the west of town is Hove Lagoon, where the wind-surfers and kite-surfers hang out.
Should you want to go shopping, the North Laine and South Laine areas are the places to wander. The North Laine is the more alternative, with clothes/sweets/bric-a-brac/fashion/kitsch/music and lots else (including many random cafes). There is also the Churchill Square shopping centre if you want to see what all the big chain stores look like.
Finally there are several internet (and video game) cafes about Brighton, but if you've got a laptop there is also free wifi access on the beach between the piers if you've got a laptop (part of piertopier.net, a community group run by lots of computer types). There's semi-free wifi in lots of coffee-shops and pubs around town (there's a company called loose-connections that offers this, but lots of places do).
The main classy tourist attraction in Brighton is the Pavillion, which is well worth having a wander around (I'm not sure how much admission is though). The Pavillion was built for the Prince Regent back in the 17th or 18th Century, and is impressively bizarre.
However the main tourist attraction in Brighton is the Palace Pier (which they've renamed Brighton Pier after allegedly causing the other pier to fall into ruin). It's got lots of arcades and rides and high-sugar foodstuffs, but worth a walk down just for the view of the town.
Also right near the pier is the Brighton Sealife Centre, which is fun in an aquarium sort of way.
A bus ride of of town is Devils Dyke, which is a valley in the South Downs (the hills that surround Brighton to the north) - it's no Grand Canyon but there's lots of nice walks on from there.
Brighton has a few museums too, the best of which being Brighton Museum right by the Pavillion (fashion, local interests, design and a really good ethnographic section). There's also Hove museum along New Church Street, and up along Dyke Road there's the very strange Booth Museum of Natural History (and stuffed animals). I almost for got the fishing museum on the seafront too, which is equally random.
There's not going to be much free time I guess, but if you are having time either side of the course to do sight-seeing there are several things you can do.
The tourist information office in Brighton is right next to Brighton Town Hall, and will have details on all the tourist attractions in the area.
Obviously there's lots to do in London, too much to list here. There's meant to be a really good exhibition of Russian owned Art at the Royal Academy, and I think the terracotta soldiers are still on display at the British Museum. Train is probably the best way to get up there, but bear in mind that a return fare costs almost twice as much if you travel before 9am.
There is lots to see and do in Sussex too, though a lot will depend on the weather (which is famously unpredictable). If it's good there are lots of good walks along the South Downs. There's a good walk from Cuckmere Haven along the Seven Sisters to Beachy Head and Burling Gap, for which you can catch a bus to and from Eastbourne to walk along.
If you're after doing something a bit olde English, the Weald and Downland Open Air Museum near Chichester is really good too, but you'll probably need to rent a car to get there.