At a guess, I'd say he's using
Latest fuel prices
The prices are well out of date. AVGAS prices vary wildly from month to month.
Yes, GA aircraft are handled by Weston Aviation just like they are at Samson at EGNT.
Weston charge £10. Last visit to EGNT cost me £25.00.
The landing fee is not included in the above price.
EGNV = £8.66 per half tonne or part of
EGNT = Minimum charge £27.00
Charges based on aircraft MTOW. Average spam can 1 to 1 1/2 tonne.