If you are travelling across Europe from Calais or Dunkirk, look out for the Q8 service stations along the E42 in Belgium. Not only do they sell the most delicious croissants for breakfast (try the cheese and ham filled ones!) there are decent grassy areas to walk your Cesky Terrier.
If you need to use the loos, do that first. It will cost you 50 cents, but you can get that back when you buy something in the shop or cafe.