Clothing for a big built boy aged 8.

[CeliaFate]

I've got him trousers from Next, Fat Face, H&M and M&S in age 10, but they're getting tight on his tummy and getting them over his bum is starting to be a problem.
Where can I get roomier clothes that have a bit of give?

Have you tried Gap? they have adjustable waist bands on many jeans and trousers for boys which helps me in finding pairs that fit & are comfortable.

British home stores do a generous fit style online for age 8-16 boys, I think m and s do the same.www.bhs.co.uk/mall/departmentpage.cfm/bhsstore/224128/1