Go for something fairly plain – a lot of the more ornate cheap watches are heavily “inspired” by stuff in the ££££ bracket…
Seiko and Orient make the best cheap mechanicals watches. They also make the entire watch, which pretty unusual – most Swiss makers will buy in the mechanical movement. I can vouch that the movement used in Seiko 5 is incredibly reliable and is capable of being very accurate – I think I’ve had my 5 for at least 5 years, worn it whilst working on cars, dropped it etc. and it’s still ticking along nicely. That said, out of the box, there aren’t many Seiko 5s which are knock out good looking.
The nicest looking cheap watches I’ve seen in a while are the Accurist vintage range and the Daniel Wellington range:
I have to say that the DW range looks great, with very thin cases akin to a vintage dress watch, but they have zero water resistance, so they’ll need treating like a vintage dress watch…
If you fancy a vintage dress watch, the Poljot / Sekonda De Luxe is nice and can be picked up for under £100 on ebay. Lots of these were sold in the UK as Sekondas, so repairs etc. shouldn’t be a major issue.
That said, I own several nice mechanical watches, including a Poljot like the above, but the watch I most regularly wear is one of these:
I love the juxtaposition of a bog basic Casio with a gold tone finish… It’s a kosher Casio (people do make fakes!), and was £16 from Singapore via Ebay. The time keeping is stupidly good, and the day and date is always right, which is ultimately the reason it gets a lot of wear.