You need an archtiect, not a website, to help design it properly firstly and secondly to help you achieve permission.
I have done one for a pub, another for a house and several for a larger house - you definitely need permission for a Bay Window.
If you are widening the opening as opposed to simply dropping the cill, you will need an engineers input to sort out the structural beam overhead.
Beware of builders who claim they'll do it all for you for nothing - without drawings, details, PI cover and competent professionals you are wide open, even for a bay window.
ONQ.
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All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.