Choice of alternates
Clearly it has been a while since you were correctly immersed (or perhaps I should say immersed to the correct depth) in the JAA IR training environment, bookworm
I'm surprised that the ops rules under which the flight is to be conducted are not made clear. The JAR-OPS1/EU-OPS criteria for alternates are different from the UK (and ICAO Annex 6) requirements for private flights.
If the flight is to be operated as a commercial flight, I would expect the alternate chosen to be commercially expedient, and close enough to make any required alternate fuel not too much more than minimal. For a private flight, I would expect any legal alternate to be acceptable.