This is a 'standard' St. George pattern set, with a 4 1/4" king. In good condition you should expect to pay £200, if smaller, damaged, then considerably less.
This is a standard Regence patern set, 4 1/4" king, expect to pay about the same as the last set.
Comparison of pieces, St. G on the left, in each case.
A 'standard' barleycorn set. 5" king. Expect to pay £250.
If you see a set where the Kings and Queens are not 'barleycorned', then it's not a 'barleycorn'.
All the rooks on this set should have flags.