For anyone interested in future:
With the door open, there are screws in each corner holding the oven to the cabinet frame. With those removed, pull the oven forward.
There are then six screws holding the control panel in place. Two underneath & two at the rear of either end. With those removed, the control panel is free. The timer is held to the front panel by plastic tabs top & bottom, be careful not to break them.
The issue with this one is that rather bizarrely, the buttons for setting the timer are integrated into a plastic frame. Yes, something that sits directly above the oven is made entirely of plastic. Unsurprisingly, this had distorted with the heat, locking the buttons. I've simply removed it for now & used a matchstick to set the clock once it was all back together. I'll research spares sites for a replacement, but that will presumably just deform again.