By "counties you need were not there" I assume you mean the Family History Societies for those counties were not there.  I agree that the number of FHSs  was down on last year, but it's not cheap for the FHSs to take stands there and no doubt even more expensive for the commercial stands.  The further from London the individual FHSs are based the more expensive it gets with travel costs and for some overnight accommodation too.  I think that all the major Home Counties FHSs were there.

WDYTYA seems to maintain it's popularity but most other family history fairs have seen a significant drop in numbers attending over the last couple of years.  How the change from Fri/Sat/Sun to Thu/Fri/Sat at WDYTYA will affect numbers remains to be seen.  It will probably suit the big commercials (no Sunday overtime to pay!) but for the county FHSs which are generally manned by volunteers it could be difficult if those volunteers are normally at work during the week.