I expect the 30mb reading was taken after the govenor at the normal test point. For some reason Transco engineers seem to love doing this, but all it proves is that there's something coming through the gas pipe! If he'd opened the ECV a bit slower it probably would have read about 26.
As...
Yes, but it will restrict the water flow slightly. How about using push fit plastic pipe instead? Should give you a better flow rate and be fairly easy to fit.
There appear to be so many things wrong with that meter installation! If the meter is outside the building the bonding should really be at the first point the gas pipe enters the building, and not in the meter box. It's a good idea for the meter to be labled to tell the competant person looking...