This can be a particular issue on the Saloon and Coupe since the clearances at either end on the ending and gearbox are very small.
I have done the cam belt on my 2+2 and needed to drop the offside of the engine down to get the bottom pulley off. Just releasing the mounting was not enough however a good firm push on the top of the engine did the trick. It is a bit of a game though as you will find you have to lift the engine up and down to get the belt in place and the covers back on. Then the bottom pulley. I have the two piece belt cover on mine so I think this made it a little easier. The only thing to watch for is anything getting a bit to taught when lowering the engine i.e. cables , hoses etc.