Here's my back-saver idea: Remove driver seat, insert plywood sitting on door sill and centre hump, ad blocking outside the car to keep the plywood from teetering. Easy to sit down outside the car and lie back. A head support would hacve been handy too to ease neck strain. Plywood was about 4 feet long.

I spent the better part of a day this past week rebuilding and converting a pedal assembly to work with a late booster/master which requires a different brake pedal and spring. Working with two assemblies I found it best to have both on the work bench. I have quite a collection of pedals and assemblies. Having the steering column out is required. Suffering lower back pain from laying on cross member with head under dash. Steve (CTR)

Undo & remove the two clevis pins from the master cylinders. 
Undo & remove the nut on the end of the pedal shaft. 
Slide the shaft out and the pedals will fall out.
Reassembly is the reverse.

 It's possible on a RHD car, but you need to drop the heater to have enough room to get the shaft out (I did it last year).

Without actually trying on a LHD car, I don't know if there's enough room to slide the shaft out without hitting the inner wing...

Here is a diagram of the assembly. Item 2 is the pedal bushing that may be worn on your car. You can also see the shaft #8 and nut #9 that the clutch and brake pedals are on. I have not looked to see if there is room to take the shaft out while still in the car. The hard part would be the spring when putting it all back together. https://www.minimania.com/CatPage/3-9/3/9/0/Clutch--Pedal-Linkage

           How do you change a Clutch pedal on a 1993 Classic Mini without pulling the entire assembly out?  Mine rock when you push it. Not sure how to fix it, but figure once removed I can figure it out.

 

                                                                    BOIB