Calorlite Availability

Preparing to return to caravaning after a 15 year break and have noticed that Calor now supply gas in lightweight 6 kg cylinders.  Not too happy that I will have to pay out for a cylinder refill agreement and understand and that this is not transferable between groups i.e. if I was to buy a Group C Calorlite 6 kg propane cylinder, I would not be able to exchange for a Group B 6 kg propone cylinder without entering into a further agreement and suffer the associated additional cost. Seems there is little choice in this matter without going down the route of other systems.  However my question is quite simple, is it advisable to go for the normal cylinder or the Calorlite as regards availabilty.  How easy is it to get replacement Calorlite bottles both on CC Sites and at Calor stockists?