Far be it from me to defend freeholders, but VB’s situation does show the value (!) of having a third party to administer leases and compel people to chip in their fair share of communal works. The threat of big legal bills and, ultimately, lease forfeiture might get your downstairs neighbours to reconsider their options.
To play devil's advocate. The freeholder has not done anything to check if the roof is sound or if any maintenance is necessary. Based on the reported damage/disrepair, one would assume that they have not even thought about the state of the roof for a long time.
Far be it from me to defend freeholders, but VB’s situation does show the value (!) of having a third party to administer leases and compel people to chip in their fair share of communal works. The threat of big legal bills and, ultimately, lease forfeiture might get your downstairs neighbours to reconsider their options.