Treadigraph, Glad to see someone enjoys the show, I've spent several enjoyable hours skimming along the South Downs...
BRL, Given you're in Brighton, I assume you are either going to Parham, or Ringmer. I'm a member of Southdown GC, at Parham and they fly Wednesdays, Fridays and weekends. Fridays are set aside mainly for trial lessons so that may be your best bet. That said turn up any of the days before 9am and ask for the duty instructor, and you should be airborne fairly quickly (i.e. before lunch, gliding involves absurd amounts of hanging around)
As for memorable flights, I don't have a huge number as I've only been flying for just over two years, but so far there is flying along a sea breeze front at 5000ft at the end of a 5 hour flight, thermalling with buzzards, scraping away from the ridge in a weak thermal to cloudbase, floating in a gentle wave system at 3000ft kicked off by the downs, soaring for an hour in weak evening thermals (never worked so hard...)
Have fun,
John