Not wanting to throw a spanner in the works, but commercial energgy agreements differ MASSIVELY from domestic gas/electricity agreements. Most large gas agreements carry what is known as "take or pay clauses". These vary in their thresholds, but 80/120 is not uncommon.
What this means is that the site is contracted to use a minimum of 80% and a maximum of 120% of its nominated AQ (annual quantity). In short, the supplier reserves the right to charge the site for 80% of its annual quantity regardless of its usage. i.e. at £80k per month, thats a minimum £768k for the year regardless of whether the site uses it or not.
Some suppliers will reconcile this on a monthly basis with an average daily load calculation, some will reconcile it at the end of the year, so clients may not be aware its coming.
The bad news is that if its reconciled at the end of the year, there would be a massive outstanding balance on the account come contract renewal time, if this cannot be cleared in one payment, then at contract renewal the current supplier would not allow the transfer to another provider. Effectively they would then have the company over a barrel with regard to its next contract price.
If the company is considering using the "savings" from simply switching off the gas to continue paying staff, I would be making sure they know the detail within their supply agreement. I know of two suppliers that will contract with no minimum consumption level, one of those will only do it when pushed and given assurances of the load, the other is not a well known company, and would perhaps not take on the risk of a construction related business with such a large AQ anyway.
Wow - did not know that, very interesting