UK Landlord Forum / Life

I bought the flat I am living in last year. It's a building with 2 flats and the other landlord and myself have an equal share of the freehold.  The landlord rents his flat to tenants. 

Here's my situation:

When I bought the flat, I negotiated down the price of the flat based on a homebuyer's report and subsequent inspection which revealed issues with the roof.  I then hired a company to carry out the repairs for £2500, which I paid myself.  I (perhaps foolishly) did not chase the other landlord for half the money. 

The roofers subsequently said there were major issues with the flat roof which they had not been able to see before- gaping holes and green mouldy growth, and the think the flat above mine is full of mould and water damage and is a health hazard.  (I have some as well).

In addition, the tenants upstairs are using the flat roof over an extension to my flat as a balcony to dry their laundry.  This area was not intended to be used in this way and there appears to be structural damage (cracks) due to excessive weight. 

The landlord has said he doesn't have money to do any repairs. I have only been a home owner for a few months so am new to how these arrangements work. Here are my questions:

1. Can I force the other Landlord to pay for his fair share of the roof repairs?

2. If yes, can I argue he should pay the full cost of the flat roof repairs (£1800) as I already spent £2500 on the pointed roof?  Or do we have to split the £1800 cost?

3. Can I ask him to force his tenants not to use their balcony? 

I think this Landlord is taking advantage of the fact that I am a first time homeowner who is interested in sprucing up the building (I also spent £2,200 on new front patio on front of building), but just don't know what I can do!