RichS

If your other windows are from the same company can't you just measure the width of the glazing beads inside. Alternatively measure the overall width inside including glazing beads, less the visible area outside, then knock off 8mm to allow for the glass packers, and you have your answer.

Start at the ridge and work down, simples !

Presumably you could cast them in at the pour stage, Not sure how the coursing would work out though.

The time taken to hang a door will vary greatly depending on how good the frame has been installed, also the weight/size of the door. if hanging internal doors I always hung all the doors first and then went back and sorted out the furniture.

Surely you can work this one out for yourself!! How many can you lay and point in an hour, how many in a m2, how much do you want/expect to earn in an hour/day. Answer these questions, do the maths and you have a price. Never mind what others charge.

Personally I would purchase another short piece of 150 x 150mm oak to match what you have there. I'm assuming the stairwell is approx 900mm wide so a piece of oak at approx 1100mm would allow you to house it into the existing 50mm and then give a wall bearing of 150mm. This would go where you have drawn the red line and the "wallplate" would not be required beyond that point (assuming the stairwell is open up to a wall which is beyond the photo shot) The bottom 50mm of the trimmer would also be left exposed into the room below to match what you already have.

A double trimmer is just two pieces of floor joist cut to size and fixed between what you have there. Do you have a piece of the oak left?. At 150 x 150 you could use that, house it into the existing floor joist and knock a hole in the stone wall to carry the other end. Why is that floor joist on the wall continuing right along the wall??, surely this is going to be the stairwell.

You need a double trimmer across. You could fix it using joist hangers or you could house it into the oak joist and hang from the wall joist. You can then infill the rest with another short joist to carry whatever flooring you are using. This is only a very general answer as without knowing what finishes you are having where it's hard to give a definitive reply.

Muti-finish/skim plus cement 50/50 does the same

You can just increase the "go" on each tread in order to make it suit the opening. This will also make it an easier staircase to climb. This is assuming that the measurements are not stupidly large.

Usual way is to build up with full bricks to no more than top of rafter level but don't do any cuts. When the roof rafters are on, but before felt/lathing run a short length of tile lath over the last two rafters top and bottom, projecting out to face brickwork. String a line between these to give the desired line for the cuts and then infill.

Doesn't matter. I would start on one side and just work across giving each sheet the correct overlap, cut to suit and tie together. You may find that laying the sheets in a particular orientation means less cuts but that's just to make things easier.

The timber has shrunk (not expanded) as it has dried out in the sun, a not uncommon problem nowadays, even with merchant bought gates. Pity he didn't form a full length tongue instead of biscuits. Won't do any harm to cover over the gaps with something like tile lath and just stain in to match. Best to only put fixings into one side of the lath and then it will still allow movement as necessary.

Oops, my mistake. I thought it was lead ?

Lead-lock, but you'll need a bit more working space.