Columbus in need of repair

Hello. I have a 2012 Superb with a Columbus Unit fitted. 
 

Just before Xmas the unit cut out and the speakers started thudding. At first it only happened for a second or two but got progressively worse to the point it was thudding constantly and the unit not powering up.

I’ve been told it is a processor that has failed, but the person who was going to fix it has let me down, so I’m looking for alternatives to getting it fixed, preferably in or around the Yorkshire area. 
 

Any suggestions or advice gratefully received!