I'm sure you've seen the group test already going by your shortlist but here it is if you haven't:
https://www.tyrereviews.com/Article/2020-All-Season-Tyre-Market-Overview---32-Tyre-Braking-Test.htm
At the end of the day, the top few tyres in the group test will be much of a much and equally as good as each other. Find the best deal and just go for that.
The 215 50 18 is -1.5% in diameter and circumference of the 225/50/18 which isn't much. On camskill in the 215 50 18 you have:
Vredstein Quatrac Pro = £98
Conti All Season Contact = £125
Goodyear Vector 4 Season G3 = £146
If it were my money I'd be getting the Quatrac Pro and saving £200. We used to have the older Quatrac 5 on an old Berlingo and they were brilliant as an all year round tyre!