So the second coat has been done and I have to say that I am rather pleased with how it looks. As I knew I would have loads left over, and nothing else to do with the remaining paint, I decided to put down a thicker coat as well as paint further up the walls. I could've split the mix down, as Snags suggested, but I'd have no use for the paint in the near future so it would probably end up wasted. I reckon I had maybe a large mug full left over, vs the 1/4-1/3 of a tin that I had with the first coat. Now the paint is dry, the floor should be good and waterproof so any spills won't soak in anywhere and should be easy to wipe up or just mop out the door.
I did leave a little heater running for a while, as the drying times are all stated at an air temp of 20C and it is not that warm right now! Equally, that one little heater is enough to make the garage warm enough to work in a t-shirt so all the work that went into the roof and the insulation is paying off already.
Essentially, that is the floor done! The existing floor wasn't the worst by a very long way, but as I hate kneeling on loose bits and divots in a floor I felt the effort was worth it. Certainly I feel that the transformation from before to now has been a most positive change. The floor has only been one part of the change, with the new roof, lighting and electrics all making it a nicer and more convenient to be. Having a double socket every 4' may seem overkill, but it will save having cables trailing everywhere which is another pet hate of mine!
I do have a new door seal strip to fit at some point today but that's a final finishing touch. I hope that this thread has shown others one way of doing things and that a decent level of finish can be achieved with only a few basic tools and the right products. There are no doubt cheaper ways of doing the work I have, but I wanted a finish that I can expect to last for many years.