Freeholder not maintaining the block

Other

1.I am a long leaseholder of a top floor flat in a block of 30 flats.
2.I have bought this flat only 4 months ago.
3.During this time there have been 4 separate incidences of water leaking into my flat through the roof.
4.Every time freeholder organizes a patch up job.
5.Yesterday I had my own builder to climb up the roof and report. He took several pictures which show worn out roof and bad gutters.
Every time I have had the internal damage rectified at my own expense.
6.Also I am suffering loss of rent as every time I am about to let the property, this leak occurs.

Please, advise