biggurs

Hi all
This is basically an extension to an older thread started over a year ago.
When I bought my car almost 2 yrs ago the horn wasnt working. I should have taken it back to the garage but it was my own fault, was quite busy and with one thing or another I missed out on the warranty period.
I noticed there was no fuse and the fuse just happened to be lying in the glove box. I put it in to the right place, I think it was fuse number 28 and all was well. Then the horn went mad and stayed on constantly so I removed the fuse. That would explain why the fuse was in the glove box- someone had taken it out because of that same problem.
Anyway, I put it back in and it was ok for a bit, passed the MOT and again the horn went mad so I removed the fuse once again.
Now its time for my MOT again and now when I put the fuse back in the horn sticks immediately.
Have got it booked in for next week for the garage to fix it before they do the mot.

Is there a horn relay on my car?
How can I access the contacts on the steering wheel.
I need to remove the air bag module and there is a tiny hole behind it which apparently you press a thin screwdriver into which then releases a spring enabling you to remove the airbag module.(I will disconnect the battery before hand)
What should i be looking for? I know there is a plug with 6 wires of which 2 (green and purple) are for the horn.
How would i know what the horn contact plate looks like and how to tell whether its faulty?
Cheers