I never usually give anyone advice about anything but, as you've asked.
I'd avoid proposing during a night out as it might be seen as being prompted by alcohol. Better to do it in the late afternoon when you usually feel content but excited about the night out. I'd suggest an afternoon tea at Betty's which is an absolute delight. It may not be your 'cup of tea', if you'll pardon the pun, but it's a lovely sophisticated place that women love. There's a mirror there, from WW2, that's quite romantic and the perfect place to propose. Speak to them and say what you're 'proposing', they'll make it really special for you ... congratulations in advance mate.
https://www.bettys.co.uk/cafe-tea-r...=google&utm_campaign=local&utm_medium=organic
And if you don't fancy that I'd suggest one of the lovely side chapels in York Minster, she would never forget that and would absolutely love telling everyone how romantic you were.