Sound Proofing Company Sought for Flat

I'm looking for a company (Brussels or Brabant based) to provide and fit sound insulation between me and my neighbours above. I've done a web search but found very few companies indeed; and some of these only provide the materials and don't fit them or else only deal with big clients.

I know it's very costly and complicated and possibly of limited effectiveness, and that some of the solutions would require my neighbours' cooperation, etc. Despite all this, any recommendations of companies would be very gratefully received.

Thanks.