You'll have to do the Olympic distance if you want anything resembling a lie-in Spans. Even then, the race needs to be over quite quickly, as although the race has a good record with the town, us triathletes have to be out of the town centre (where the run is) sharpish to let the tourist do their thing.
Windsor is voted the best race in Britain year in, year out, with the exception of Llanberis' first year (2001). It's on my definite list, despite my nightmare this year. (Despite a headstart of an hour, I only beat Jodie Swallow by about 15 secs! The crowd gave me a right ovation. They must have thought I was one of the elites!)
BB