I'm not gonna lie as soon as you said £15 and concrete I was put off lol I'm more akin to £8 -£10 with an orange Wednesday deal in VIP seats. Me & the gf sorted!
Those mats are very cheap if you don't mind them saying toledo on it. Check you have the oval twist caps though, I think the sx has oval ones but I can't remember what the other type ones are so I'm not sure.
The dark blue and tinted windows do/will look ace.
What size alloys? 16, 17, 18, 19? 20 even? lol I think 20's would fit but you would have a ridiculously low profile tyres that would cost a bomb and ride quality would be shite as well as slowly ruining your gearbox/clutch...might look cool though

and bear in mind once you put alloys on that are bigger the car looks like it sits a bit too high for the wheels.