I’ve had a Mini Mac, they’re a nice little box that does pretty much everything well.
Windows 8 is actually rather good now that the 8.1 upgrade has been issued. A lot better than XP, the Metro interface doesn’t need to be used at all so if you don’t have s touchscreen, then you don’t need to use those features.
In general 8.1 is faster, more reliable, has support, and is a bit nicer to use than XP. It is arguable that Win7 does all of this too, and I would definitely advise an upgrade to 7 if you don’t fancy 8…. however I upgraded to 8 for £15 direct with Microsoft.
Pc and Mac are definitely choices, you seem to have bought into Apple in general, so I think your question is more: “Why shouldn’t I buy a Mac Mini for £350?”.
If there are no good reasons, then do it.
Or spend £15 on a Win8 upgrade. This will not, however, get you a Mac.