Roller doors are a top upgrade. I love mine. They improve security, convenience and help insulate the place a little better. I would do this first.
If there’s an internal door, I would insulate the garage so you can leave the door open and have it heated. Makes it much nicer to work in (if you’re going to have a workbench).
If you’re going to install a workbench I would give serious thought to electrical, ie make sure you get enough high ampage sockets pit in a convenient place, install Wi-Fi, usb sockets etc.
I used an epoxy resin floor coating for ours, again love it, really smartens the place up and makes it easy to wipe up spills. Do this at the very end to avoid it being damaged by other works.
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