The SACU is the ACU. Scotland is just a ACU centre.
Why it has a different name, offices, fee system and the likes i don't know. I'm going to make myself unpopular here but I do question what membership of the SACU/ACU actually bring me other than hastle and cost. I've not known any one claim the insurance it provides and maybe it's great but knowing insurance companies it'll be nothing special. As it happened I have Personal cover that would support me so it's only 3rd party cover that's being added by the organisation. I could find public liability insurance for my local club members at less than