Hello Raul,
You have no legal right to refuse payment of repair costs incurred by the lovely old council on your behalf, unless you can prove the work was over-priced, not needed etc. In other words, the council acted fraudulently, negligently etc.
Big trouble has been brewing over council leaseholders that bought into the homeownership myth perpetuated by that silver-haired monster back in the 80's and 90's (yes, I'm talking about the Lady Thatcher. If I've offended anybody...).
Councils have been poor at dealing with their money and haven't had the funds to do up council estates. The latest wheeze is to go private, by transferring whole estates in need of repair to Government quangos (Housing Associations) which can then borrow money, get big grants (bribes - or regeneration grants) for transferring and then implement major capital works to the estate to bring the blocks up to today's minimum standard. That means new kitchens, bathrooms, new roofs, new lifts, new services and lighting, new parking facilities, new playgroups or community centers and associated community things and so on. You as a leaseholder will pay for most of that (not the kitchens and bathrooms etc of existing council tenants) but the bigger things to the block and possibly the surrounding areas. If you live in the flat as a leaseholder, your charges may be capped. If you are an investor and let your flat, there is usually no cap, unless you lie to the council and say you are living there. Be careful on this one for those of you that are sub-letting and haven't informed the council. The best thing is to check your lease and see what you are or may be liable for.
Some blocks won't be as pricey as ?20k though. I have an investment property in London E3 that I am looking to sell soon that will cost only ?6k approx. That is what they (the Housing Association) have intimated and looking at the amount of work involved I believe them. Thankfully mine doesn't have a lift, which is usually the killer.
I would advise getting in touch with your local Leaseholders Association for advice. You should be a member anyway to support them as they help many council and private leaseholders.
Thank you
Harrison
