Loft insulation application rejected

I was a bit puzzled to receive a rejection from Octopus to have loft insulation upgraded. Their reason was “we were unable to find an installer”. I have a standard 2up 2down terraced house, nothing outrageous was being proposed. They said I can try and contact an installer myself from the GBIS installer list. So I was wondering if anyone had loft insulation done (or underfloor, or solid wall) and can recommend an installer in the north?