Don`t panic!
Here is what I know and what could be helpfull to know for every participant:
-England:
Don`t know about the fines there but since we don`t drive a long distance there I don`t care. Just don`t forget to drive on the wrong side of the street.
-Belgium:
Seems like the politicians here aren`t the biggest car fans but since it`s a small country I suggest two options:
Drive gently and enjoy the view, maybe take a short stop for some french fries with mayonaise OR
Full throttle and no second thoughts about Belgium`s slow police cars and the possibility that they impound your car. (It seems that impounding is only possible for citizens of Belgium but I don`t want to try that out.)
-Germany:
-Well if you aren`t german: Have fun! You will find lots of parts of the Autobahn with no speed limit. And with no speed limit we germans mean: Absolutely no limit. You can push your car to its very limit, even if it`s a Pagani or an Enzo. If the speed is limited there are lots of controls with anything you can measure speed with. We have lasers, radars and undercover police cars. Bavaria even has Helicopters that can measure your speed. The fines should not be too bad; on the Autobahn 41 - 50 km/h too fast will cost you 100 Euro, if you are more then 70 km/h too fast that`s the highest possible fine: 375 Euro.
-
Tschech Republic :
-They flash on the highways but on the other roads should be no controls. The fines should not be too bad and the police is happy about bribes.You have to buy a toll label.
Hungary:
-Lasers are used here and for fines see Tschech Republic.You have to buy a toll label.
Austria:
-High fines that have to be payed in cash. If you try to bribe the cops they can send you to jail for one day! Rumours say that the police there is aware of the Gumball and that they are using all of their police forces to control it. You have to buy a 10-day toll label for 7 Euro 60.
-
Kroatia:
-Few controls, bribes welcome. Very good highways.
Italy:
-Some controls with expensive fines. Ferrari and Lambos will have a small advantage...

Don`t know about bribes.
France:
-Since 2004 they have a little problem with the Gumball. Better keep it down because it`s only a short drive through France. The highway from Italy to Monaco is very beautiful.
In some European countries you have to carry warn vests in your car but the fines shouldn`t be too high...
Overview on fines in Europe:
____________Alcohol limit__20 km/h too fast____overtaking
Austria-----------0,5-----------20-55.-------------70-145.-
Belgium-----------0,5 ---------+ 150.- -----------+175.-
-
Croatia -----------0,0 ---------15-70.- -----------30-70.-
-
England ----------0,8 (

) +95.- -------------+95.-
-
France------------0,5 ----------+90.- -------------+90.-
-
Germany ----------0,5 ------upto 35.- -----------30-125.-
-
Hungary-----------0,0-------upto 120.- ----------upto 80.-
-
Italy --------------0,5 --------- +140.- -------- -- +70.-
-
Tschech Republic-- 0,0 --------- 15-60.- -------- +15.-
-All fines in Euro. :p
-So if anybody has any additions or corrections to make, please do so.
Drive fast, die happy!