Hello Crya,
When the body shop gets it, there will be a lot of removing of parts. Wings, doors, boot and bonnet. There may be some welding needed. Let's say the areas in front, below or the rear of the door. Welding makes sparks and you don't want any sparks to land on your interior. The windscreen will have to come off. That means the dash top before the windscreen. When the door are off, best to have the interior door panels off too, to protect them form abuse. If you have the rug in, that will need to be covered. Don't want sparks to burn it, and it will collect all the dust in the body shop. The body shop will spend more time trying to cover up, protect your interior than you may want to pay for. You don't think those man hours will be free do you.
Have the body shop paint your car. Bring it home or to your interior guy last. A good interior guy will know to be careful installing your interior.
Ever watch the TV series American Hot Rod. Boyd Codington built some amazing cars. The interior guy always got the car after the paint guy.
Cheers,
Roger