No Central Locking - Discovery 2

I have looked through the threads, but can't find one matching.
I have just bought a discovery 2 van and the central locking does not work at all.
The key locks and unlocks the drivers door only, the buttons on the key fob do nothing other than light the small red light on the fob. ( I only have one key)
There is also a flashing red light on the dashboard which the seller says is connected.
Really need to fix as the van has the bulkhead fitted so if I lock the rear doors manually there is no way to get back in to unlock them

What about the central locking dash switch? no effect either? ... anyway you can't do much to fix this without proper diaagnostic tool ... the engine starts or it's immobilised as well?

The engine starts and runs as it should. Can't see a dash switch, but will have another look.

The switch is on the left side of the clock

Just tried it the switch doesn't do anything!

Check fuse F1 interior fusebox eventually get hold of a same type fusebox and replace it cos it's a common failure.