Welcome to the forum, this may answer some of your questions.http://www.elevenplusexams.co.uk/school ... ol-11-plus
As to tutors, unfortunately there is no regulatory body for tutors. The best way is to go on personal recommendation.
I am not from the area so am not familiar with the 11+ in Wirral. Hoefully someone will come along who has local knowledge. Meanwhile have a look around the rest of the site, There is a lot of information available.
The papers are Verbal reasoning so lots of word games, eg scrabble allowing use of a dictionary, boggle and ww.freerice.com to build up vocabulary will help