I painted both the garage floor and the bio shed in Screwfix floor paint.
The garage has a very smooth finish in high strength concrete and has survived well ... circa 8 years. The only areas that have suffered are around the lathe, mill and drill where swarf gets trodden into the finish.
The bio shed lasted only a couple of years despite trying to mop up each spill and drip immediately. I replaced it with some very tasteful blue tile pattern lino which has survived quite well, but is now starting to pucker up around the most heavily trafficked area.
Jim ... if you have a source of cheap polyester floor resin, I'd love to hear of it. I spent a considerable time looking for cost effective coatings and all were way more expensive than floor paint.