You have a nice little garage there. Mine was similarly dingy looking, but had the advantage of already having a boarded out ceiling - this makes a hell of a difference, especially for reflecting light down. I painted my bare brick and block walls with standard "trade" paint - think it was the trade emulsion from Wickes. Did one coat 50% water using a spray gun, then one coat over that with a big fluffy roller and a masonry brush. On it's own, this made the whole room much, much brighter and more pleasant looking. Combined with two new 6ft LED batons, it's so much nicer in there.

I also painted the floor using a two part epoxy paint - did two coats of this, after sweeping and hoovering the floor clean, and chipping and scraping off any old residue and mortar from the previous owner's use.

If the garage keeps getting leaves and other guff blown in, you can get weather seal for the threshold which fixes to the floor. Also useful if you find rain gets blown in as well.

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I'm not sure how this sub is for links to Amazon, so the floor paint I used was called "Epoxy Floor Paint by floorsaver". The garage threshold seal thing I'm planning on fitting is called "Stormguard" and can be got from Screwfix or Toolstation.