Our tenants have just moved out and the wooden floor is looking really quite grimy, especially in the hall. I'm thinking that we are going to have to sand it down and revarnish but wondered if there were any steps we could take before we went down that route - any suggestions?
Well, if you're prepared to sand/refinish, then you can afford to try washing it with some strong cleaners. The main risk to washing wooden floors is water soaking in and warping the wood. You'll want to avoid that. Don't let water stand on the floor for any length of time. You can avoid that either by keeping the amount of moisture low or using wet vac to pick up any water before it can soak in. (You can rent one at a tool hire place.)
I would try scrubbing the floor with a brush in one hand and wiping it with a cloth in the other. It requires getting on your hands and knees, but it's effective and will give you the most control over how wet it gets. I'm not sure what cleaner you should use... I'd be tempted to tell you to go ahead and use Stardrops or Flash or some general cleaner like that. Fairy could be good, too, but don't let it get too sudsy. Mix the bucket with cleaner, get a good pile of cloths (microfibre are best but expensive because you'll use a lot of them. Old towels/tea towels will do.)
Dip the brush in the bucket and scrub in a circle in front of you. Scrub, scrub, scub... then wipe with the cloth in your other hand. This will pick up the grime and remove excess moisture.
You can mop the floor but have some old bath towels to hand to throw down and scooch around the floor with your feet before the floor gets soaked. This could work on less grubby areas.