You need to slide a thin bladed knife under the Nylon strip the supports the PCB and slide it along to release the little catch in the strip, and it all slides out.
When looking a the opening and the strip is at the bottom, the catch is on the left hand side
Have successfully done this thanks.
Beware any non technical readers - this pcb contains some very small components that can be easily damaged. The support bar is nylon and is not that easy to remove.