Update.
My order arrived from premier range, all packaged well and came in a couple days.
In preparation for attempting the cutting myself I bought a scriber from toolstation for a couple quid.
The upstand glass is as thick as the toughened glass at 6mm. The upstands feel very very strong.
Cutting
I used a slightly different method to apcbob, I used a square and used spring clamps to hold the glass in position, I think a square is a better tool for this as you can be sure you're getting a straight cut. I found that after around 15-20 firm passes of the scriber was enough, then position the glass at the end of the bench you're working on and give it a firm push just past the cut and it should snap cleanly.
Putting on wall
Pop a couple tiles spaces on the work surface against the wall and if its butting against a cabinet one there as well,
offer the cut piece to the wall and check see if it rests plumb.. if not then remember where where and then apply more less silicone in that area..
apply silicone (they say you must use there silicone which I purchased to be safe but a mirror adhesive will be ok i'm sure)
press onto wall.
That's about it really, i still have to do a bit around the boiler but overall I am very impressed, 5 metres and a splashback and their adhesive for under 100 quid (i caught there sale) which was a few hundered cheaper than 2 glazing companies quoted, in total will take around 2-3 hours to fit in a kitchen of that size and anyone can do it so saves on tiles, adhesive, mess and a day or 2 for a tiler... i can see why tilers aren't a fan of upstands now.
The only downside I really see is that the lengths are only 1m so you will have a seem if you have a wall that requires a length greater than 1m/1000mm, its not really a show stopper and as with most kitchens you could just put the kettle or sugar jar in front of it if it really bothered you.