Basically the answer is the only real biological research conducted in the UK in the past twenty years is
DecodeME, its still taking people in. You need a diagnosis from your doctor so that limits the audience to about 10% of all ME/CFS patients and they seem to be rejecting lots of severe patients with comorbidities for DNA collection but its about the only real research being conducted. The rest at best is some impact assessment and is healthcare useful and at worst its still CBT/GET nonsense or some obesity.
If you can do DecodeME I think its got potential.
I think my main concern is that smaller DNA studies have found nothing, admittedly based on the existing biobanks so there is every chance its garbage data but there is every chance its not really genetic based. The impact on anyone personally however is a short swabbing and sending a small package back from home so its doable for almost everyone. They also wanted 25,000 participants but that is very unlikely given the estimated 265,000 UK ME/CFS sufferers of which just 10% have a diagnosis. This would require participation of near 100% and that isn't practical.