Anybody who has managed to convince you that the fitting of these doors is straight forwards fabrication task has seem you coming a mile away and had a good laugh in the process. I promise you any remediation work on any ex-BREL piece of rolling stock is an absolute nightmare. It's hard to find words for just how badly built each and every one of them is, and just how much no two coaches have ANYTHING in common. From doors to handles, nothing fits anything but the coach it came from. Even the interchangeable air con and brake modules can't be interchanged, because the majority of the rafts only fit the coach they were built for. We would recruit for months on end for any staff who are competent or even capable of adapting their hand to this type of coach work and they're non-existent. Nil. We would recruit for months, in the middle of Derby, and get nowhere.
Having delivered 15 plus C6 overhauls of MK3s I feel nothing but pity for our brothers at Wabtec, forced to live the nightmare that is nailing sliding doors onto a rotten old Mk3. I sincerely hope that their contract is not too damaging from a liquidated damages or consequential loss perspective. No company is going to touch these doors with a barge pole and there are no magic pools of trained fabricators to save them from the challenges they currently face.
MK1, MK2, MK3 and all the rest of that tat is only favored by those who don't have to fix it. It's hopelessly unsuitable to adaptation to PRM requirements and the sooner they're cut up, the better.