Had a look through the sizes (you had them as a 40, they are a 45 profile 
) and no snow tyres to fit 
You could do what I did - buy a set of cheap Alfa alloy wheels off ebay and bung some nice narrow(er) high profile snow/winter tyres
I thought all MiTo had a 40 profile on 18" rims, but there you go
Even getting normal tyres is not easy for it as they are ZR rated so the bog standard Pirellis it comes with are £160 each and rarely stocked, normally V rated.
This is a pet irritant for me, so bear with me whilst I have a moan
You are not going to change the way the car drives by fitting V rated instead of ZR - let's face it, you're unlikely to be doing over 150mph (more likely up to 150mph in a Tb
) and even if you do fit V or W rated tyres look for those with the additional XL rating as they have reinforced sidewalls and are more than up to the job if coming down in speed rating. It's a conversation I have had many times over the years and more recently had with my insurers (LV) last year and they agreed that provided the tyre fitted is legal (obviously) and the same size as the original it doesn't matter one jot what the tyre rating is as the UK speed limit is 70mph. Same went for snow/winter tyres as, in my case, I've fitted 15" alloys with the Alfa recommended tyre size of 195/60/15 and the tyres are 'T' rated instead of 'V' rated as the handbook says they should be in that size. They are legal and that's all that matters - the speed rating really
doesn't matter in the real world, it's a tyre salesmans wet dream though
My 17" alloys are tucked away in the shed and will not appear on the car again until May.....by then I
might be able to afford a new set of 215/45/17s
As for Alfas, they may have a "few" issues but by god they are fun to drive 
When it's working (which to be fair it is now) I have to admit mine is an absolute hoot
H
