Another good afternoon in work resulted in the passenger side door finally coming off as well as the front seat belts getting removed and the rear door cards getting taken out.
The first job was to have my 3rd try at taking the door off, but so I had more space, this time I decided to jack the car up and take the wheel off, which I must say made the whole job much easier. After taking the wheel off and lowering the car almost back down to the ground to make it more stable, I tried to wipe as much of the dirt off the bolts as possible to hopefully allow them to come off more easily. After another dose of CorrosionX, it had done the trick. It was possibly one of the hardest things I have ever done in terms of effort needed, but eventually each bolt slowly came off. I found it easier to crouch by the side of the car with 1 hand pushing onto the bolt and the other hand turning the handle, while I rested my shoulder against the wing to give more force (while being careful not to dent the wing!!).
After doing this to each of the 4 bolts which hold the door on, and about 1 hour or so later, the last one had finally come out. After this, make sure you have space to put the door down as it is pretty heavy (about 20kg) and you don’t want to drop it!
The next job was to remove the front seatbelts which I couldn’t manage to do yesterday, due to not being able to work out how to unbolt them. However after some playing around today, it became clear that the cover just pops off to reveal the bolt. I have attached 2 pictures above to make it less confusing for future reference!!