Weather diversion or no weather diversion, £360 for a Seneca is armed robbery + buggery.
Having taken the Seneca they will probably loose the revenue for a Hawker, plus the fuel, plus the handling, plus the catering +....
It is the local governments/councils that set ridiculously low movement caps that treat a jet the same as a light piston. It almost forces the airport into being jet only. (Which in no way excuses the practice of some airports that are not capacity constrained that price or administer GA out just to simplify their lives)