you may get more replies on the bizjet/GA forum, however it depends how many pax, how flash you want to be etc etc...
You could try Diamond Executive Aviation at Gamston; they operate DA42s for passenger charter - probably about the cheapest option if only 1 or 2 people, or Ravenair Liverpool may be able to help with a PA34 or similar.
You could also try Capital Air Charter at Exeter, who have KingAirs; there are a number of other operators with similar aircraft too.
You probably won't get an operator to lay over unless they're really quiet, so you'll likely be looking at 2x one ways; there are various operators of larger aircraft such as KingAir or small jets...a search of the Air Charter Guide website may help:
Air Charter Guide - A Definitive Resource for Online Aircraft Charter
For small jets, Centreline at Bristol, London Executive Aviation, Blink at Blackbushe, Gama/Hangar 8, Flairjet, Airmed Oxford (to name a few) are all options, but probably more expensive.
h14