Car Diagnostic Supplies

Hi,
I am just about to buy a used peugeot 206 02 plate for £1200 but the central locking is not working which means they cant get in the boot. This has only just happened and after a diagnostic test, it apparently needs new motors on each door (3). Does anyone know roughly how much this would cost to supply and fit. Just want to know if its worth buying the car in the first place?
Thanks