Most modern blocks have a management company. Decisions are made are made and residents have to comply. Much, much easier in the case of repairs, anti-social behaviour, etc. My son lives in a converted house and basically paid for some repairs to the roof himself as it was so hard to get the others to agree.
Bear in mind that if it is a newer block (this may apply also to converted houses, I don't know) there will be a service charge. This can be pretty hefty so check it out.