I have the same issue. I need my gas meter lowered by approx 1 metre. Told by SP to contact National Grid. Pretty useless advice. Trying to find the correct department or telephone number at National Grid is proving ridiculously difficult. Their website and that of Citizens Advice both state categorically that the Supplier should be responsible. Any real advice would be welcome.
According to what I've read on the internet, it is the supplier who is responsible i.e. Scottish Power. Unfortunately, their Customer Service seems to be severely lacking. I've had no end of difficulty getting through on the phone, and when I do, I end up being shunted around, and often promised a call back which doesn't happen. I'm trying emails now and will resort to letters if I get nowhere. Very frustrating.
I have had similar problems and as a last resort I sent an email to the CEO of Scottish Power and got a fairly quick response. I was told that I couldn't move my gas meter then I was told that I would have to wait for a time slot from Scottish Power. I eventually contacted Cadent, who actually carried out all the work and they did it in 4 days of my request. What is more I was informed by Scottish Power that the money sent by Cadent to purchase a new meter had been added to my account because "they" thought a payment was being made on our behalf by Cadent. I asked them why would Cadent be paying for our gas and electricity - no response and the operator just hung up. If it's gas I suggest you go to Balfour Beatty because they act very quickly.