A few years ago I tiled a penthouse patio in London. It took days for the adhesive to set. I was using Toppfix 2 part.
a couple of years ago I tiled a room in a very cold house. The tiles next to the radiator set very quick. The tiles next to the patio doors were still moving 24 hours later.
If you go ahead and tile in those conditions then you are asking for problems and headaches. Unless of course we have a change in our British weather system!
OK, I know you wanted ideas, but we don't know what the ramp looks like. Is there another way of getting to reception?