i did quite a large area of floor in front of sink on our last caravan about 3 years ago, bought the ready mix option off ebay, it came with a srynge, easy to follow instructions, plastic plug and dowels. Its easy to do but messy and the fumes are really bad. I was going to use the plastic plugs to cap off the drill holes but they were slightly rounded on top and i wanted to put laminate down afterwards (i thought I might as well replace the carpet whilst doing the job) If you use wooden dowels to cap off the holes, you can cut them down completely level with the floor once its all set.
I am not going to repeat the method as given in last post but just remember a few key points before you start -
check you are not going to drill into any pipes or cable,
get everything ready before you start including rags or kitchen paper and large bin bag.
give yourself a very large clear work area
make sure there is a lot of ventilation and use protection.
allow time dont rush.
It took me less than 2 hours to get the carpet up (I was replacing the carpet so i cut it round the fixtures rather than gently pulling it out) prepare the area, do the job and clean up afterwards. i left the roof ligts open and windows on security catches and fumes had gone by next day. A couple of days later I spent about 20 minutes cutting a few ends off the dowels and sanding down.
the results were great, no more spongeyness, level floor and it cost no more than