The economics of this deal do not seem very harsh, to me. I think we are all ingrained with typical military thinking, where everything costs lots and lots:
In order:
7 aircraft use for 5 years each. Typical dry lease arrangements would be less than 1M per year per aircraft to place them on station, buy them, and set up hangar/shop kits. That is $35M for the fleet
Typical need would be 5 pilots per aircraft and 5 mechanics? Plus maybe 3 more admin/shop/schedule per aircraft? Call that 13 people per aircraft, full time. 13 x 7 x 5 = 455 man years. At about $150,000 per manyear ($75 per hour, including all benefits) that is $68 million.
If one assumes 250 hours per year, fuel is at $4 per gallon, that is $900 per hour, plus $1000 per hour for maintenance (atan assumed power by the hour rate) you gat 1900 x 250 x 7 = $3.3 Million
Assume insurance at 4% per hull value per year = $19 million X .04 X 7 x 5 = 26.6 Million
I don't know if the hangar is provided, or is paid for, lets assume each aircraft costs $50 K per year to hangar = 50K x 7 x 5 = $1.75 Million
Totals 35 + 68 + 3.3 + 26.6 + 1.75 = $135 million
Add 20% profit = 1.2 x 135 = $161 million
Convert to British pounds = 161/1.76 = 92 million pounds.
Buy a hedge for the dollar vs pound at 2 Million, and laugh all the way to the bank, with 7 million pounds for incidentals and unplanned expenses.
PS I did not assume the AB-139 was cheaper, but it should be about 70% of the S-92 costs all the way around, making the above calculations conservative, by far.