I live fairly near Cambridge and there aren’t really very many unfortunately. Mappin and Webb have Rolex, Omega and PP. They are on the market square. Then there is Fraser Hart in the grand arcade which stock Tudor.
There is a small jewellers next to the Round Church that stocks Nomos.
And the other place that I look at is the window of F Hinds (believe it or not!) at the grand arcade entrance. Alongside the quartz dress watches they have a small used section of some nice watches. Rolex etc. Above RRP obviously though, if that interests you.
Hope that helps.