CAP168 Chapter 3 Para 5.2 refers:
The length of RESA needed for a specific runway will depend on a number of variables, such as the type and level of aircraft activity, and local conditions. The minimum requirement is 90 m for all code 3 and 4 runways, and code 1 and 2 instrument runways.
Para 5.3 also states that ideally it should be 240m & if less a full risk assessment would be required each year as part of the airfield safety case / SMS.
Leeds is another airport that faces similar challenges I believe.