Not sure of any statistics but I know one inspector who spotted 4 false entries in a log book (simply because he remembered the weather on the day in question) and it cost the holder £1200 (1996 prices) and no ATPL issue! The £400 figure was quoted to me as an average by an ARE enforcement officer who said courts understand fraud, but are more lenient with people running out of fuel! The figure varies from court to court.
but wondering if the CAA actually care.
If they spot it or suspect it, they are duty bound to pass it to ARE for investigation!