Push button type toilet takes the cistern up to 2+ hours to fill.
Could this be an air lock?
Can someone please suggest a solution.
Alternatively if this is not the problem, could someone please offer cause and solution?
As you may gather... I haven't a clue!!

Air in the line is not the problem You have a defective fill valve, or at least a defective washer or seal in the fill valve. Your fill valves over there are a little different than ours, can you describe or show a picture?

push button type toilet takes the cistern up to 2+ hours to fill.
could this be an air lock?
can someone please suggest a solution.
alternatively if this is not the problem, could someone please offer cause and solution?
as you may gather .... I haven't a clue!!!
Let us know what type of ballcock,(see images) and we'll get right back to you. Regards, Tom