Manston

[ExpectmorePayless]

As far as I am aware, there are currently no fees for nominating a diversion airport in the UK. Airports are open for normal scheduled operations and can accept diversions during these hours subject to capacity.
It was purely a suggestion to fund the operational expense of London Manston (terminal, handling, fire service, ATC and security etc) given there is unlikely to be sufficient revenue from planned aircraft movements alone. A relatively modest flat fee multiplied for most flights to London airports per year should generate a significant amount.
Obviously, if an aircraft did divert and land, it would also pay the more significant landing, parking and handling fees. As would any scheduled movement.

This practise is used in the more remote areas of the world, whereby airport facilities are made available outside of normal operating hours for consideration as ETOPS diversion airports. The airport operator will by prior arrangement extend published operating hours and provide the necessary fire fighting, handling and ATS facilities for a small nominal fee.

In this case, the fee would be an extra cost to the airline but could be offset by the reduction in fuel costs, assuming less distance to divert and elimination of holding requires less fuel to be loaded.

UK airports (such as Durham Tees Valley) often downgrade fire fighting and ATS facilities outside of operating hours for scheduled flight movements. If there is enough demand from airlines to use the airport as a diversion airport outside of operating hours, then it could in certain circumstances generate sufficient additional revenue to extend the hours during which services are provided. Difficult for Durham Tees Valley due to it's location, but probably easier for London Manston being sited near to a major multi-airport hub with 6 London airports supplying traffic.
In 2018, there were 1.1 million aircraft movements to LHR, LGW, STN, LTN, LCY & SEN airports. That's £1.1 million if all flights were charged a £1 fee for using Manston as a primary diversion. £11.8 million if the fee were £10 per flight. Diversion fuel for a flight diverting to Manston from let's say LGW would be less than if it diverted to STN.