j0hn nice find with that ECI firmware version, I must have missed that post, interesting there is still activity on ECI firmware, but not so good that it possibly is the cause of the US regression for the OP.
My recent experience in contacting openreach I would actually say has been positive, I get the impression they are as frustrated as us with lack of direct contact so will try to do what they can instead of saying something generic like "contact your CP".
They will probably appreciate the feedback regarding the dslam firmware change, so I advise again to try openreach directly. Its very unlikely a direct resolution will result, but it could lead to them looking into it more even if they dont tell you that.