Hello and Welcome...
My name is MIKE - Im happy to help / advise you ..
Im afraid when you have this situation - as you say, its extremely difficult to do the job without damage to the card... but tips would be - to help avoid that .. to move the front seat forward out of the way - and remove the rear bench seat - that gives you that much more room / access to work on removing the door panel..
It can be done - but it is difficult - The only other way, is to use a garage or recovery firm ..or Aa / Rac - if you subscribe to them - who have "lockout kits" - who should be able to open the door for you using the kit - down inside the door.. through the window seal.. Once the door is open, it makes it so much easier to remove the panel. But other than that - you would need to progress as above.
Im sorry there is no "easy" fix or way forward - but those are the options for you to make the job easier..
Do get back to me if you need anything else at all -
Kind Rgds - MIKE....Meantime..............Please do click on the "OK/ Excellent ratings" for me as that's how Im credited for helping you - Thank you in advance for that...You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..Rgds, MIKE.