Does anyone know what the max size is for the crufts benching please?

It depends what breed you have, as there is a minimum size per breed that is allowed

we take a 30 inch cage and it fits in perfectly. Not sure if all benching is the same size for different breeds though? We show staffords

The benches do vary in size depending on breed. My breed has a minimum width but last year some benches were larger than others. It can depend on which breed is in the same area the previous day.

we take a crate every show (just in case) but our girlie prefers to lie on the grooming table and watch the world go by!