I rode the 2004 (my first 400) and 2005 versions.
The 2004 was organised by Pam Pilbeam and had controls Denmead- Lockerly (an El Supremo feed stop if I recall correctly) - Lymington - Blandford - Lockerly - Denmead (for a sleep stop) - Whitchurch (another El Supremo feed and very welcome) and back to Denmead. There were stiff headwinds out to Blandford and a fair bit of rain.
The 2005 version I think was organised by Mark Rigby, from Apperley and went up Stanway Hill before controls at Alcester, Tenbury Wells, Presteigne, Bwlch, Alveston, Brinkworth (both of which had some sleeping facilities) before returning. Nice weather from memory.
I've blogs of both events if you want more info. And I think my account of the 2005 version was in an Arrivee shortly afterwards.
I really liked the format, especially the midday start, as a 6am start for a 400 often ends up in an early hours finish, but for one reason or another have never managed one of the reincarnations.