uPVC Doors - Install Advice Needed

Hi All
I have a couple of questions regarding 2 things i need to install.

The first is a door i have that i need to install, i have no problems installing it but i think i will need to raise it about 40mm in order to get it at the right level (its going in an extension and not put the floor in yet. I was going to angle grind some slabs i have lying around to get to the right height, is this the right thing to do or is there something you can buy for this purpose.

The second thing is some french doors i have. These are two glass doors with two double glazed windows on either side ie 3 actual things to install. I have got the alloy 'joining' pieces that i think need to be screwed together to make on big unit and then install. I think that these need to be secured using self tapping screws but unsure of this part. Is this the right thing to do (I can't find an installation guide for this type of install)

Thanks

Lee

Cut some bricks in half instead of using slabs

Use self drilling 'bay pole' screws to screw the frames together

Clamp the frames to the aluminium couplers then screw the Baypoles through from both plastic sides.

I’m doing this today too, i’ve done it once before but might have done it wrong by screwing through the aluminium coupler first.

I’ve seen this since that says to go through the plastic side first:


From here:

https://www.windowwidgets.co.uk/downloads/brochure/?brochurepage=4