cases are very subjective since the are determined by personal aesthetics... but out of those 3 I think the xigmatek looks the cleanest... (I personally don't like my cases junked up with a ton of plastic and I'm sure many people here will recommend a case from the HAF series)
What hardware is going into it? I'd hate to recommend xx case only to find your graphics card won't fit in without the angle grinder getting involved
bothered about mesh or acrylic side windows or lights?
£40 is a narrow budget for a quality case but there are gems out there,
check Scan, Dabs and Ebuyer as well for bargain cases
This isn't going to be an expensive build. Air cooling, very rarely there is going to be CrossFireX/SLI and it will have an ATX motherboard. Not bothered about a side window but no lights. I wanted this to be a quality case because in the future I want to re-use as many parts as possible to keep payments to a minimum.