Will my car fail the M.O.T if I put my own horn and switch in my car as originally doesn't work All steering wheel controls nonfunctioning?

Hi all… I have a Honda Civic 2009 and all the controls on the steering wheel no longer work I think the clock spring is broken and I think it will be very expensive to get fixed. I don't use the radio controls or the cruse control anyway. So I was thinking about buying and wiring up a horn safety and securely with a a 12v battery And a switch on the dashboard to pass the MOT…
would this be an MOt fail?
Can you have a horn on your dash board or is it compulsory to have it on the steering wheel?
Is a clock spring hard to replace?
Any tips I would really appreciate thanks
Any idea of the cost to have it replaced or should I just wire up a horn?
P.s I've checked all fuses it's not a fuses or relay problem?

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