In reply to imkevinmc:
> You dial 999 and let the emergency services make those decisions.
The operator answers the phone, and says "what service do you require?" They then expect you to say "police", "fire", "ambulance" or maybe "coastguard". They are not really equipped to help you choose.
To the OP:
Call 999, ask for the police, then ask for mountain rescue. If you are better off with the ambulance, they will pass the incident over to them. The ambulance service on the other hand are not always great at calling out mountain rescue. This is just because the Mountain Rescue often call out the ambulance to take care of the casualty once they have got them to the road, so are familiar with them and what they can do. Ambulance personnel on the other hand rarely have to ask for MR help, so just aren't as familiar with their options.
Even at a crag 500m from the road, remember that an ambulance comes with only two paramedics and a gurney with wheels. Injured people are kinda heavy, so half a dozen MR guys with a stretcher designed for carrying might be useful even there.
Post edited at 20:57