I have several warning lights that come on when starting that remain on, Electronic Stability Control, Tyre Pressure Light, ABS Light,  Power Steering & Bend Lighting Function (AFS). 

They confirmed a sporadic fault in ABS, which may be down to a communication issue withe the BCM. Can anyone give me an idea of the cost of a new BCM, and is it easily accessible?

It takes two to communicate, why decide that the BCM is the problem, rather than the ABS module? 

Who are 'they'?

Arbury Skoda dealership 

All those faults sound like a failed ABS sensor, a very common fault 

Take it to another V/W independent garage for a 2nd correct diagnosis👍