I'm unsure about the other parks, but for August, accommodation for Europa-Park (be it on-resort or off resort) needs to be booked in the new year, and flights need to be booked by Easter for those planning on flying to Strasbourg with Ryanair from Stanstead.
Just thought I'd post this because we are nearly in December already!
1. Helix
2. Wodan
3. Nemesis
4. Blue Fire
5. Balder