Final comments are to reiterate that your proposed gas pipe will form part of the common property, and whilst it will not encroach on another person’s Lot it would be somewhat difficult to maintain without trespass in the absence of a sky-hook, so I’d suggest some degree of caution about you relying entirely on a consent regarding access to that Lot from the current Owner that would not apply to any less-friendly future Owner of that Lot.
You’d do better to rely upon the means discussed in the 7th para of my last post.