Had to take mine off to investigate another lovely new engine sound.
Did not expect the mother of all ball-aches that was getting the ******* thing back on!!!
So, after trying all manner of bodge techniques to get enough force on the tensioner whilst at the same time slipping the belt back on - I came up with the following method...
1. Fix a 15mm spanner on the tensioner bolt head (with the other end to the front of the car)
2. Find a bit of rope...
3. Bend the rope in half - http://i.imgur.com/SYXxO.jpg
4. Lower the mid section of the rope down the side of the engine - http://i.imgur.com/H5fza.jpg
5. Loop the rope through the other end of the spanner - http://i.imgur.com/wruBD.jpg
6. Tug on the 2 ends of the rope like **** all-mighty
7. When you're about to burst a blood vessle, grip the ends of the rope in one hand and hold on for dear life
8. Slide your hand down the side of the engine, find the belt and slide back on the tensioner
My greatest ever bodge and it was literally the only way I was able to do this.
Hope this might help someone in the future!