Having new tyres fitted on my car

Question

This will seem like a daft question...

I'm having 2 new tyres fitted on my 2000 Daewoo Matiz. Looking at prices of tyres, they range from £30 per tyre to £45 per tyre.

Would there be any harm in me having the cheaper ones fitted? I'm only going to be keeping my car for 9 months-18 months max.

What's the difference between cheaper tyres and expensive ones?