We used the Mercure Dortmund to break up a long drive from Germany to the UK, the roads around the hotel are a bit of a maze but it was found ok with sat-nav. Some of the hotel's parking was out of use so we had to wait for someone to leave to get a space, but it was free.
Staff were very friendly and spoke good English, room was a nice size with free mini-bar items, and good bed & bathroom. Starting to look a tiny bit tired around the edges but still good standard for the price.
Unfortunately we were given a room overlooking renovation works and the work started at 7am, including pneumatic drilling... so not the most relaxing wake-up call ever! In hindsight I should have asked for a room higher up or on the other side of the hotel, but as the hotel didn't seem hugely busy it would've been better if they sited guests away from the building works or had them start the 'heavy stuff' later, as after a couple of hours the workers started quietly gardening!
The air-con also seemed not to be able to cool the room sufficiently, and we had to have the windows closed due to the building work.
We weren't there to see football or a concert, but this hotel would be a perfect choice if you were.