Hi and welcome.
Clitheroe, LGGS and LRGS all sit the same papers on the same day. The schools get together and write a Maths and English paper. As you say the Verbal Reasoning is obtained from and educational foundation.
My daughter sat and passed the test last year and she starts LGGS this September
and we too live outside the catchment area so I know what you mean about competing for a very small number of places!
If you look on the LGGS website under "Admissions" there is a PDF with information about the Entrance Test and a list of different papers for Verbal Reasoning which may be worth looking at.
There are also two Maths and two English past papers which are very helpful. It gives you an idea of the lay out of the papers.
Hope this is of some help and best wishes to you and your son! At least you get to find out if they have been offered a place within two weeks of taking the test!