Fencing in communal garden

Hi all, I hope this is the right place to post this!
I recently moved into a first floor maisonette which is share of freehold. I'm in the process of becoming a director of the management company, there is one other resident (out of 6 maisonettes) who is the other director. There is a long history of all of the other residents not contributing any monthly contribution towards maintenance and only the two directors contributing despite repeated attempts to get the others to pay. This is what I have been told prior to moving in. I think 3 of the maisonettes are rented out.

I want to get a dog and have been told that I would have more chance if the communal garden were secure. The garden is accessed by an alleyway between the two buildings which is open and ungated, there is also a short fence on one side with a gap that a couple of the residents use as a cut through. In order to get a dog I would need to get higher fences on one side (the other sides are already adequate height) and put gates in where the gaps are. I am willing to pay for this myself (dependent on cost!) but I am wondering if anyone can advise on whether I need to get the permission of all of my neighbours regardless of whether or not they are contributing towards upkeep/maintenance? Ironically the neighbours that are not paying are the only ones that actually use the garden (they have children) while the cost of gardening/mowing the lawn comes out of the maintenance fund.