From an article in The Telegraph by Allison Pearson, these phrase translations from English English to American may be helpful for those about to travel in the UK for the first time.
Not bad = Good
Good idea = Bad idea
A very interesting suggestion = You’re clearly insane
We were a bit disappointed to hear... = You cannot be serious
I’ll bear that in mind = I’ve forgotten it already
Perhaps a few minor adjustments = Tear it up and start over
By the way… = The main topic I need to raise…
We should think about making a move = Get lost!
Sorry, is that your bag? = Move your stuff immediately
Bit nippy = Do not go outside
You really shouldn’t have = What the hell were you thinking?
Here is the source, FWIW. https://bit.ly/2sFS23v