Greypaper

Hi guys I have purchased a new house and the driveway seems to be sinking in the areas where cars must have been sat on! We were advised that since the biggest dip was directly under the drain hole cover, that we should get a drains survey done however the survey came out fine. The house was only built 20 years ago and most of the houses in the street have similar sinking. I was looking to get this sorted however we would only want to do a cheap fix as we are low on cash and doing it properly would probably mean getting it filled underneath, we also don't know how long we will be living here so we don't want to invest much into it. It seems like there are 2 areas where it is sinking (on the left where the drains access is and on the right, probably the 2 areas where cars were parked) and the builder told us that he would be able to patch it up with tarmac, this would keep it going for a few years and he would pour some liquid or something over it to help make the whole driveway look the same colour. Can I get your opinions on what would be the best, budget solution? I have included some photos here on Dropbox as my photos went over the limit . https://www.dropbox.com/sh/sznrlzlz3y3o9r0/AACYrMZtikvTrOT6DMXd4rAua?dl=0