Any ideas or suggestions please as to why the central locking in my 94 wagon is only working from the tailgate?

Can you give a little more information?
By 'only working from the tailgate' do you mean it's only the tailgate that unlocks when you use the remote (which suggests the actuators on the other doors are all U/S), or do you mean that all doors only lock/unlock when using the key in the tailgate?

Ah yes sorry I mean all doors only lock/unlock when using the key in the tailgate