When I had mine done I actually installed the White box myself, which
saved a few quid, though that was not part of transcos job. After I
placed the order they put me in touch with the local depot, I drove
there and picked up the box (no charge). Just a little information that
may be of help.
As an aside I also had the electricity box moved, at greater expense
than transco, for, in my view, less work. Now they keep ringing my bell
for access to read my meter, can't get it into their little computer
system that's it,s outside. Tried everything, even the different
supplier is the same. Gas people got it right from the start though.