I've just had a quick look on the national grid website, the process has changed in the few months since I applied for my new connection. There was no option at that time to fill in the application online, it was all done by post. And there was most definitely a discount at that time for pre-digging the trench myself. In my case I had almost
40Metres to dig and the cost was considerably cheaper doing it myself. The other factor is that my house is detached and it would make no difference to the meter reader whether the meter was at the front or the back, but it made installation much easier as we didn't need to cross any drains etc.
None of this helps you of course, but what I will say is that at some point a surveyor will have to come out to asses the work that needs doing. At that time you'll get to speak to somebody who hopefully can use a bit of common sense to decide whether what you want is practical/ allowable or not.
A new supply is treated much differently to an alteration. Yes you get a considerable discount by providing a pre-excavated trench over the private part. Alterations are discouraged by the pricing policy as they don't add to the profit line
The reason goes something like this:- The gas transporter, National Grid has its profits capped at 7.5% of its asset value. Its assets are mains and services. A new service (supply) adds to the asset value. An alteration does not add to the asset value.
mark