In BMW Car Mag this month it states you need rear mud flaps fitted for driving in Poland.....
My Lonely Planet guide also states:
Warning Triangle
Tow Rope (proper tow rope with eyeleted ends, not ordinary thick rope)
Fire Extinguiser in car cabin fixed to secure bracket and easily accessible (ie not behind seat but underneath front is ok)
If you wear glasses, A spare pair of prescription glasses (not sunglasses) to be kept inside car cabin (Belguim)
Spare bulbs (inc Xenon if you have them fitted)
Spare fuses
High-Vis Jackets - 1 for each passenger to be kept in car cabin
First Aid Kit
Blanket (Germany/Holland)
Rear Mudflaps (Poland)
Both Parts of UK Driving Licence
Insurance Documents inc Certificate (not copies)
GB Sticker or licence plate with EU blue bar and UK or GB in yellow print
It is illegal to run ot of fuel on the Autobahn
If travelling through Luxembourg, you have to flash your lights if overtaking at night
Good luck with the trip, the Salt Mines are well worth a visit near Krakow