The 10k is at Hillingdon Cycle Circuit on Sunday 2 September. Details and entry form here. Closing date for entries is 28 August.
According to John C’s site, this is also the Inter-Counties championship for this year. If you haven’t anything else planned as a target race for the end of the season, this might make a good candidate. A bit early, but the Leicester 10k on the 16th Sep isn’t (yet?) a BMAF championship race this year.
The 50k is at Colchester on Saturday 22 September. Details and entry form here. Closing date for entries is 17 September.