Get yourself a proper sized box. Why do you need such a big one for a pair of wheels?
A double wheel box is roughly 65x65x30cm.
Parcelforce will take that, no problem, as will most other couriers, for £20-30
But, to where in Eastern Europe are you sending? Most won't send to Russia, for example, while Belorussia or the Ukraine are OK. Some countries have a reputation for parcel contents disappearing...
Give a man a gun, and he can rob a bank.
Give a man a bank, and he can rob everybody.