Have you tried contacting CIGA at all? They have been responsive when I have contacted them in the past regarding removing cavity insulation from a timber framed house (yes retrofit blown fibre into timber frame). You need to make sure that the usual 25 year guarantee is still in date. The fact that the original company are no longer in existence should not affect the outcome. They have contractors nationwide (often the installers are now doing the insulation removals) . Hope this is helpful. Can you keep us posted.
The Cavity Insulation Guarantee Agency
3 Vimy Court, Vimy Road
Phone: 01525 853300