The UK tickets don't seem to have the residency requirement on them that Canadian ones do. You'd be charged in GBP£ rather than USD$ so FX charges either way. I have already bought 4 day passes using the CAD deal so can't test the process.
The only offers on the UK site I see are for 7, 14 and 21 days, but they are Ultimate tickets so include photos and are hoppers. When on the Disney ticket site, change your local to UK and you can check them out.
Quick math -
CAD Deal - 7 day plus hopper plus photos on this deal = US$632 or ~CAD$825 = CAD$117/day
UK Deal - 7 day Ultimate which is the same = GBP£365 or ~CAD$620 = CAD$88/day - the 14 day deal isn't much more total so is a really good deal if you've a longer trip
Edit - Adding to highlight this is 7+ days tickets only and it's YMMV as I've not gone through process