Okay, so AS355 has range of 276 miles (with 3-4 passengers) and 437 miles for 1-2 passengers.
Agusta 109 generic (!) ;) has range of 276 miles (with 3-4 passengers) and 368 miles for 1-2 passengers.
Dauphin AS365 has range of 512 miles for 1-6 passengers???
Sikorsky 76 has range of 489 miles for 1-6 passengers.
I think!!!
So, the Dauphin AS365, S76 and A109E would be ideal, although the Hebrides would probably be on the edge of their range (taking into consideration weather conditions, diversion airfield, diversions en-route etc.). I found a few charter companies that have the Agusta 109E Power although the Harrods one only quoted a lower range (maybe at expense of travel time/speed).
So, really depends which part of the Hebrides you want to go to. Lower part you could possibly make it, but northern then no chance I reckon.
Kempie, part of EADS Eurocopter is 1 mile from where I live ;)