I notice no or almost no difference between the pronunciation of these words.
Are they really pronounced the same way?
(not a professional teacher) In the interests of clarity of meaning, they probably should not be pronounced the same way, but they often are. At least here in NZ, I would say that they are most often almost indistinguishable when spoken, and so the context in which they are used is the only means of determining which is meant.
I have an Oxford dictionary with very useful pronunciation symbols (IPA) written behind the words. I looked up both words and this is what this dictionary tells me:
Note that even the stress on the syllables are exactly the same. The only difference is that accept starts with a schwa, and that except starts with a /ɪ/ like in <sit>. So there is a difference, but indeed quite hard to tell when the language is spoken in its normal speed.
PS: The symbols are written in recieved pronunciation accent.