Hi Kate,
Unfortunately we are quite limited with the flight times that we can get for the groups of our size. We do try really hard to get you the best flight times available for your trip, for example, those people flying from Birmingham are arriving in Berlin at around 9.35am, however the flights we have from Heathrow do arrive later. I am really sorry you feel as though you are wasting a day, but I hope you can appreciate why we have done this.
If you give our Holiday Advisors a call, they will be able to tailor make your holiday and see what the availability of flying back on the Sunday is.
Kindest regards,
Monty