1998 Vauxhall Omega central locking/stereo faulty

Electrical problem
1998 Vauxhall Omega 4 cyl Two Wheel Drive Manual

Hi
my two problems are that `1` the buttons on the steering wheel of my 1998 vauxhall omega do not operate the stereo, and if I give the keys a twiddle the stereo comes on but if I go over a bump it goes off again I have noticed that if you bang the steering wheel it goes on and off, I was going to have a look for loose wiring but cant get the steering wheel off.
my second problem is the central locking is not working, I have tried putting keys in and turning till the lights come on and then pushing the buttons on the keys but its not working I have done this before on my other car when I accidentally pressed the buttons on my keys. I hope I have explained my problems well enough for you.
many thanks
Stan