Some time ago I extended my bungalow after drawing up plans and receiving permission from the council. I’ve now been told I should have informed the council about a change of use. I’m 73 and don’t want to have to sell up.
It sounds as though the council isn’t so much objecting to your extension as to what you’ve been using it for. If you’ve been using it to run a business you should probably have applied for planning permission not only for the structure but also for a “change of use” if the business is noisy, annoys your neighbours or involves a lot of people coming to visit you. Whether the council can do anything about it may depend on how recently you put up the extension. If it was more than ten years ago they cannot start enforcement action.