I'm looking for the same things, similar budget and live in the UK too, I know sounds weird to me to. Also £400 is $681.65 CA or $647.81 US
Linus has mentioned this monitor on his channel & the day after on NCIX's channel (this one got me into watching LinusTechTips back in April)
I think that's the Canada/US version, back when I saw the videos linked above I did some research and found there are 2 UK versions of this monitor. Going by model number the UM.VH6EE.001 & UM.VH6EE.005 are available from Amazon UK and going to the Acer UK doesn't really help to compare the two either since a recent revamp <_<
Since I haven't managed to build my new Video-Editing WS yet due to a roof issue, I am still looking around the same budget at £350 for 2 monitors ($596.45 CA or $566.83 US)
So any more help will be welcomed
EDIT: Not trying to takeover thread, just didn't see the point on starting a new one for a very similar question in the "Displays" forum