Have a look in London first.
Red Dot cameras.
Aperture UK - near British Museum
There is place on the Strand near Waterloo bridge (I forget the name).
If you dont get it serviced when you buy it, you will need a service within a few years. I prefer a service when I buy it.
They are all good. My preference is M3 for 50mm lens. I have the .85 viewfinder on the M6 which is good for the 75mm and a .58 viewfinder on an M7 for wide angle lenses.