The bed linen wasn't kept from 5A. The north door doesn't seem to have been tested for anything, neither was the outside of the bedroom window. The main bedroom, half of the living room, the kitchen and bathroom weren't checked at all. A bit late now for a new forensic sweep, I would have thought.
The only samples that may remain somewhere are the hairs that didn't correspond to the haplotypes of people known to have been in that flat (and 6 of those from the bed went walkies somewhere between when the PJ forensic team photographed them and the PT lab so they weren't even analysed). Even if one of the haplotypes found corresponded to this guy, it would just include him as a possibility, but wouldn't positively identify him.
IFFFF the missing hairs from the bed could be found in a dusty PJ box somewhere, and one or more had roots, then a nuclear DNA test could be done.
(I'm aware that there has been research into extracting nuclear DNA from hair shafts, and on occasion it has been successful, but from what I've read it still seems too hit-and-miss to be commercialised, and requires quite long hairs.)