Bikenut, this thread has some links to various places that make straps, and some cases, too. Some are not retro at all while others might fall into that style, depending on your tastes. https://www.mu-43.com/showthread.php?t=451 I do not think, however, that any are in the UK. It appears that most of the leather camera artisans are either in Japan or Italy.
I'm in the market for both myself.
How do you protect the LCD screen or don't you? I'm really thinking about when it's in a camera bag if you don't have a case that protects it.