It's called a glottal stop:
https://en.wikipedia.org/wiki/Glottal_stop
Jennifer - Apologies if you already know all this.
I'm assuming there won't be a great deal of dialect involved so as to appeal to a broad audience. But one thing that grates as an avid reader is when an American writes an English character but has them using American colloquialisms or terms. Even for "standard English", I'd hazard some American writers feel they are having to relearn a language they thought they had spoken all their lives and that becomes doubly complicated when attempting to place a character geographically in the UK and it come across as authentic.
A specific example for your character. An English meal would involve a starter, main and dessert/pudding... only really pretentious places would refer to entrées (which means starter - I understand it used to mean "main course" in some parts of America) and only American restaurants would say "appetizer".
It does stand out... two countries separated by a common language and all that. I would ensure you have a friendly Anglophone on hand to check for any oddities before publication.
In terms of football fans, we are almost universally creatures of habit. We tend to meet the same people, in the same pubs, drink the same drinks, leave at the same time and sit in the same seats from August to April/May when the season ends.
Language tends to be "industrial"... as you may have gathered if you read the forum... as football evokes strong emotions. If he's a Blade, your chef will be battered and a bit world-weary. It comes with the territory (both being a Unitedite and being a chef... most of the ones I've worked with have been miserable sods

).
No... it doesn't. I can vouch for the veracity of the OP thanks to the limited checks we do on allowing new members through.
People are very unduly cynical of new members... not a very Sheffield welcome.