My wife is running too and yes, info is rubbish! that's fairly typical of the race for life series - she did Paddock Wood last year and there was little info (none on course) then either.
However, on day organisation was very good and I think that is typical too.
Seems start/finish is near City Thameslink station/Holborn Viaduct/Smithfields market (a fairly small area really). I'm sure we'll find it on the day. Good luck