I've used all sorts of gear down the years and mechanical (+ a battery powered meter) is my preference.
Of that specification, I'm currently using a Nikon F2S and a Nikkormat FTn. The F2 is probably the most solidly built of all Nikon's manual focus film bodies. A Photomic head (DP-1) or DP-2 (which gives you an F2S) should be available for £150 ish. I've recently bought a mint FTn (fixed head, no option to add motor drive but built like a tank) for less than £100. A slightly more cosmetically "used" version would be available for a bit less. Nikon glass Pre-Ai and Ai is plentiful, extremely good and reasonably priced.
The OM1n was my favourite camera when shooting in the 1970's / early 1980's. You wouldn't go wrong with a good example. Zuiko lenses are excellent but they can be pricey if you're looking for quick glass. However, OM1 and OM2 derivatives are lovely in the hand and only marginally larger than Leica rangefinders. Nikon, Canon, Pentax and Minolta tend to be more substantial and a fair bit heavier.