We wanted to take over a coucil run plot a few hundred years age..(so it seemed.).. and asked the council to pass on our phone number to the owner of the plot we wanted. When they contacted us and we offered to call round to collect the key and a ready written letter for them to sign giving up rights to the plot mid term , they jumped at the chance.
Some people are basically lazy and having paid will just neglect their plot hoping that their original enthusiasm will return.
Sometimes an easy opt-out in the form of a signature shoved under their noses does the trick!(..well it did for us- and that is not in line with our normal characteristics!!!!!)

Go for it ...just be very practical and simplistic!!!!