I don't think they do, even in the US. Some things can cost more to ship than the core refund. Then, you have to accept their word on it if they say the core isn't rebuildable.
I once bought a right side drive axle for the 86 from PartsGeek.Com. Core was something like $15. No way I could ship back the old one for that, so I just threw it into the scrap heap.