My sister has a Focus TDCI 55 plate, anyone know where i can get a key with the 3 button remote near bedford from and what price they are?

 

Depends if it will need programming to the car as well or do you have the means to do that.

 

is that where you turn it on and off in sequence to the dash board lights?

 

It can be, but that process (if it applies to your model) only deals with the remote locking, the immobiliser chip has its own separate activation process.
If you have a Mk1 and at least valid 2 keys the manual tells you how to validate a 3rd key & chip against the system, not sure about later ones. If you can't do it yourself you'll need a Ford dealer or auto security specialist.