I've found some posts online with similar issues to mine where it was only fixed with a 'lift and shift' and I'm wondering if moving from BT to say, Plusnet, would have the same effect. My BT contract ends next month.
Moving to any other ISP while remaining at the same address will change nothing on the distribution infrastructure, OR will have no reason to attend, all carried out remotely.
Your line however will get a DLM reset which after a few days with the new ISP will probably leave you back exactly where you started but with an alternative modem/router which may or may not be a better performer on your line.
Any VDSL service ISP you choose to use are subject to OR's infrastructure and service, with the obvious exception of cable services, some ISP's are better than others with respect to dealing with OR but that usually comes at a cost.
If OR are "happy" with the line and not willing to investigate further why not try a replacement modem/router preferably one which can produce worthwhile line stats, there are lots available S/H at very reasonable cost especially now with the ever increasing migration rate to FTTP and most migrants using their new ISP provided devices.
