UK, Ireland / My recommendation for parking at Doncaster/Sheffield airport [10]

You can travel form Retford to Donny Airport by bus, 29 service i think. Service stops at villages on way to airport. I leave my car at my parents and get them to drop me off, thats the cheapest option. Enjoy your trip.

UK, Ireland / Uk Car Insurance in Poland [6]

I would check with your insurance company that you are fully comp for those 90 days. Better safe than sorry.

Cheers