HGV handbrake valve rebuild - who can do it?

[Chris-R]

Does anyone know an HGV fitter or a company that could overhaul the Wabco handbrake valve in my old Iveco Turbozeta? I've tried putting new seals in it myself, but can't get it working right - possibly because I've put the internals back together the wrong way somehow.

My local HGV garage just wants to swap in a new one at vast expense.

[hooblah]

Got a pic?

[Chris-R]

Yep - it looks like this.