Rear brakes seized on ldv convoy mini bus?

Hi all...just bought an LDV Convoy mini bus on a 02 plate.

Drove it home no probs....just been out in it and the whole back brakes seem to have seized.

Cant drive it either forward or in reverse however much i try so it's stuck on a dodgy estate untill 2moro when i can get it recovered.

Anyone any ideas please ?

regards and thanks in advance