Ignore Cleversod, i believe if you are paying for somewhere to live, there is no point paying for it's upkeep, this is your landlords responsibility and any decent contract will say so. We have had same problems as you, and have had nothing but constant building issues!
At the end of the day you are paying for a service.
Luckily we know our current contract back to front and have read more and more on tenancy laws and know where we stand. Your contract shoud be a minimum of 6 months, and this rolls over without having to re-sign, the period it can roll on for is usually defined in the agreement, usually 1 year from signing but doesn't have to be, maybe longer. Negotiations on rent has to be signed for which is probably why you wont have resigned. It is standard practive that notice has to be given on the day of rent and is for 30 days, where this differs is for the landlord who has to give you 60 days notice from the first of month or day of rent. This will be in your contract. Just because you haven't signed a contract doesn't mean your previous one isn't still active.
If you have had problems etc, you may be eligible to ask for a reduction in rent for the problems you have had, as long as they are suitable reasons! We once had to stay at home for two days to lok after a team of plumbers and builders who were traisping round, after two days we were refunded a % of the months rent payment and incurred costs for re-heating house to deal with damp and cleaning of furniture!