The AIP is pretty clear...... Firstly, you are getting confused between "Special VFR" and "Helicopter VMC". Special VFR is simply a reduction in the normal VMC criteria which may be given to you in a clearance, normally by a Tower Controller, (but could be Approach) on request by you, . On the other hand, Helicopter VMC is available to all helicopters, carte blanche. ie; by day, OCTA, (ie Class G), provided you are at or below 700 AGL and clear of cloud, vis not less than 800m and make broadcasts in accordance with the AIP requirements. Don't have an AIP close handy to give you the exact reference but it's easy to find (ENR1.2 I think from memory). Anyway, the answer to your fundamental question is yes, it is OK for a Charter helicopter to use Helicopter VMC.
Cheers