Our uPVC 2G came with locking handles on every opening, and little plastic caps to press into the keyholes of any openers that needed to be escape-capable.
The Cuprinol stuff is very good. I did our current decking with the (now discontinued?) water-clear stuff and it worked well for maybe 3yrs. I've an unopened can in the attic to re-do it with but it's very low on the list right now...
our blockwork went up first (I had someone to do it, we did the roof ourselves) but definitely don't negate the effect of the tiles loading out the structure- our clay tiles worked out at about 7 tonnes.
sorry about the poor piccy, but we've got this. Lintel steel just resting on the cripple studs, racking steel (on a steelpost in the inside wall of the room) resting on, with the upstairs walls again just resting on. All from the drawings.
IIRC the premium uses the slightly more flexy duct.
I paid for my design, as I wanted it prior to buying the stuff (and ended up getting the unit elsewhere), I think it was £100 or £150, and it was credited against the subsequent order as I recall
I got a few sheets of 10mm XPS to do the reveals, but I've only done the bathroom windows and think I'll do the kitchen ones but don't really see the need to do the rest.
Local B&Q recently clear some 2-temperature bulbs for a few quid. Switch on as warm white 35W tungsten equivalent, toggle the light switch and they're 60W equiv cool white.