It's what gives you peace of mind that really counts Terry.
I haven't heard of anybody getting a full-sized wheel as a spare and yes you would lose a fair bit of space.
The only thing to consider is that an awful lot of XE's on 18 inchers have different sized wheels and tyres front and back.
So if you are in that camp and had a rear puncture your front spare would be narrower.
I haven't heard of anybody having issues with the space saver and your spare wheel would be doing the same job as a short term thing until you can get to a tyre shop so is the expense of a full wheel and tyre worth it over a cheaper "skinny" ?
Three years in now and there are probably plenty of stuffed XE's in salvage yards so you might be able to source the space saver and maybe even the proper "Spare wheel" boot floor to keep things tidy quite cheaply.
But up to you.
Wheels, Tyres, Suspension, Chassis, Faults and Fixes