Many thanks everyone! I know Alcantara isn't something everyone is the biggest fan of however I feel it really lifts the interior overall and anything that gets rid of big swathes of plastic can only be a good thing
If anyone's thinking of doing similar, the seat trims are by far the easiest, the headlinings and A pillars aren't too bad and just have a few tricky spots. The windscreen surround is a proper pain and getting the material to stretch correctly around the map lights is not easy! Alcantara only really stretches in one direction as well so aligning it in such a way that it'll stretch into a corner helps a lot.
The headlining comes down in two parts and is just held up with plastic clips, they pop out with a little force in the right place. I've attached a picture below to show their locations. Move the roof into the 'service' position to get the rear section off. I think the front section will come off with the roof in place however I found it easier to pop the rearmost clips then pause dropping the roof to take the front ones off. There's two little plastic trip pieces on the rear section that can then be unclipped as well.
For the windscreen surround and a pillars, first drop the roof. There's a couple of screws holding the sun visors in place, just take them off and the windscreen surround will pull off first, it sort of hooks into the A pillars so I'd recommend pulling off one side at a time, then there's just a couple of connectors to the lights/sos button and it'll come away. With that out the A pillars will pull up and out from the metalwork, there's no clips with either of these and getting them back into place is a game of just pushing/pulling until it all slots in correctly.
I did get donor items for the windscreen surround and A pillars as the first time I looked at it I thought it'd either go really well or really badly
I'm not a professional at this stuff by any means so I'm afraid there isn't much advice I can give on the actual trimming other than glue things in sections so you can pull the material into place easier around corners, I used Evo-Stik 528 contact adhesive. It's some seriously strong stuff and crucially won't fail under heat from the sun. It stinks like hell mind and unless you don't mind the car smelling like glue for a week, I'd suggest leaving trimmed parts for a couple of days before refitting them :lol:
Oh, heat guns are also handy for the really awkward bits!