To add a few details, the escape door was hinged at the top, used some sort of explosive charge to open and incorporated side panels that protected the chute structure. The chute itself then slid down another 1,5m or so. Unfortunately I don't have a photo that I can share but there is a good view in
Keith Wilson's Haynes Manual (on page 77). It was first fitted to ZA143 at Hurn and tested on this airframe. The other conversions also got this installation and it was retrofitted to ZA141, which flew before ZA143.
The escape chute having been removed, the port forward door was left sealed shut (the avionics bay access hatch is visible in the floor):
I think this is the remaining gauge that BEagle mentioned:
The door can be opened for maintenance purposes. The locking pins are retracted by using an operating handle in the fixture shown in the photo above and a tension strap that fixes the bottom of the door to the fuselage needs to be removed. The 'abandon aircraft' light in the photo above is also a remnant of the escape chute system.