The minima quoted are just that. Some ASUs may be more demanding in their requirements. 'On-shore' experience is sometimes stipulated, but that does not mean that a pilot whose experience is substantially off-shore is to be ruled out, provided he can demonstrate sufficient land-based ability.
Flying is very hands-on and the task requires a good level of airmanship, generally founded on solid Command experience.
Ex-military pilots have a lot of good experience to offer, especially in the low-level environment, but I know at least one ASU pilot, whose background is purely civil who is a very safe pair of hands and a respected operator.
ASU salaries have improved. Pilots who are directly employed are earning £40K or more (plus benefits, especially a civil service pension!) a year around UK. The Contractors may still not have caught up. This doen't equate to N.Sea salaries and the hours are long. In the Met Police area, where houses are predicatbly expensive, most of the pilots travel some distance from home to duty over roads that can best be described as unpredictable, which extends the effective 'working day'.
If it's just the money, I hear that building worker on LHR T5 are going to earn £55K per year: so there are some well-paid on-shore jobs in aviation after all!
Back to ASU/EMS. Immensely satisfying, though sometimes frustrating jobs, with lots of challenges and very worthwhile.
SFIM, if you think the cap might fit, why not give it a try next time somebody is recruiting?