We've done the Opole to England drive several times. No tolls last time we did it (apart from Opole to Wroclaw).
Our preferred route is A4 to Dresden, up to Leipzig, route 6 through Harz Mountain area (beautifully quiet and just as fast as a motorway), up to A2 and west. Eventually to Hook of Holland for the ferry. May not be the quickest. We go to Harwich but I think there are ferries to Hull as well - maybe from Rotterdam.
You could, if you got up early enough, had two drivers, and didn't have any major hold ups, get to Hook of Holland in time for the night ferry. However, we have kids who need breaks and we like to enjoy the journey so generally stop after Osnabruck somewhere near the motorway. Then the next day is very relaxed.
Detailed journey:
Day 1
Set off 5am. Bautzen for breakfast. Beautiful town, nice to stretch the legs.
Harz Mountains for lunch.
Hotel by about 5-6pm
Day 2
Hoge-Veluwe National park by midday. Spend four or five hours cycling around (expensive but bikes are free and if you like Van Gogh, the museum in the middle is worth seeing).
Stock up for the ferry at Lidl in Hook of Holland. Feel at home as it is generally full of Polish greenhouse workers also stocking up.
The night ferry is better than any of the ferries I've taken between France and the UK. Really clean and comfortable.
Coming back, again you could get from Hook of Holland to Wroclaw in one day. We generally stop near the Harz mountains (Goslar, Quedlinburg - beautiful towns). We arrive around 5pm and Wroclaw is another 5-6 hours so you could be home before midnight.
Enjoy the trip!
