Can anyone tell me what the requirements are for holding a Management Company AGM and the implication if this doesn't happen within the required timeframe
It depends on what has been specified in the Memorandum of Association for the management company. You'd have to get a copy of these and check. Usually however the first AGM has to be within the first 18 months of creation of the company and then an AGM every 12 months after.
You can report the management company for a breach of company law if an AGM isn't held within the timeframe in the memorandum of association.