I thought perhaps this had something to do with the recent
OnStream request, part of National Grid. There is an unverified entry giving OnStream's switchboard number (0121 4248000) as an alternative.
Is this regarding a letter you have received from Transco, National Grid or whatever they call themselves today saying that they require access to your property to change the meter?
Presumably you received a letter similar to that on page 277 of
this PDF on National Grid's site.
I Googled and came up with
this page that gives
01452 307307 for the address you quote.