At the end of last season, we were casting around for a course to use instead of the Stony Stratford course, which was proving so unpopular, that we mostly cancelled the events owing to a lack of interest. The reason for its unpopularity was probably threefold: it has a stiff climb on the outbound leg, there's some rough road surface which makes the high speed sections of the return leg rather unpleasant and it's a non-standard distance (11.4 miles). There's also a lot of competition for parking with loads of paddle-boarders and other river-users.
After a lot of head-scratching, we decided to adopt a course developed and used by Team MK, the Cranfield course. This begins just outside Cranfield University and runs down to Newport Pagnell before finishing near the BikeBus. This isn't a particularly flat or quick course - check the link, and see the course profile below.