disconnecting water supply to toilet

[phil_cardiff]

Argh! I have a leak between my cistern and the bowl when it flushes. I reckon it's the rubber washer between the cistern and the bowl. Can I get to it? Can I hell.

I obviously need to take the cistern off the bowl but need to disconnect the water supply 1st. Unfortunately I can't get my wrench onto the nut, pictured below, as the pan is in the way. Any ideas? It's the top nut as the one underneath it is below the water shut off valve (the little screw head).

Picture found here:
http://www.pistonheads.com/gassing/topi ... connecting water supply to toilet

Thanks in advance