I'm a big fan of the UO 8, 9, and 10 series. I've owned a few of them over the years and they are very dependable workshorse bikes.
This is my mid 70s UE 8. The bike came to me with the swept back bars so there is a mismatch between the bar and stem I'll need to sort out. I'm still working on the bike but I've semi-modernized it with an alloy crank and alloy wheels. I have a set of simplex stem shifters that I may end up using on the build if I stay with the flat bars.