In the UK, where is the best place to look for a winter Overcoat for men ?

you could try a charity shop

Hugo Boss have some really attractive ones. Just check them out...

I got my last coat from Vinted. Granted it was second hand, but there are lots of brand new with tags one on there too. Might be worth a look

I think Debenhams still have an online ordering service. Also there is a shop called Edinburgh Woollen Mills that does some reasonably nice men's things that seem to be a wider fit.

Your local Army Surplus shop might be worth a look.

You might end up with one that scrapes your ankles but it'll be cheap and very warm.

Not sure if they have any locations in UK, but in US the answer (now that Brooks Brothers is gone) is Boscov's

Slaters in Edinburgh

Well here is how you do it. Go to whatever good department or menswear specialist you can find locally and try on as many as you can, making notes of the ones you like and why, anjd the prices. Now go home and google those very coatsincluding your size.
You will come up with a short list of the places to get the best deals and may even come up with one on ebay being sold as not needed any more.😷

Brooks Brothers. Charles Tyrwhitt.

Have you tried ebay?

Mountain warehouse

Depends on budget.
Burberry is great, but costs Burberry money.

Tresspass?
M&S?