As I have already fitted a new tire to the spare wheel and painted, plus, also refitted the spare wheel tray, I set about refitting the spare back into its place.
Things did not go as per plan. The spare wheel with its newly mounted tire will not go into the space it is supposed to go into. After much pushing and "kushti" I gave up and did some investigation.
Here is what I found out. See the picture below. The spare wheel tray rests on the two chassis members indicated by the yellow and green arrows. I have drawn two horizontal red lines for reference. If you look closely at the chassis member indicated by the green arrow, it is not straight. There is a bow in middle of about 3/4". I think in the past the car was lifted from this point using a floor jack. Due to this bow the spare wheel tray sits too close fuel tank and to the space is not enough to accommodate the tire.

So now this chassis member has to be straightened before I can proceed to the next job.