Comment: check your legal options (Score 1) on 2009.08.11 5:19
I hope you have documented incidents such as the feces and the lack of cleaning. Continue to document any similar things which occur. In many countries, if they fail to live up to their obligations, you are justified in ending the contract early. I'm not sure if this would be the case in the UK, given how much the country likes to get exemptions from EU protections, but you might consider looking into the matter.
Also look at what the maximum legal penalty is for breaking the contract--it may not be as much as they've written in the contract. I find that landlords and employers often like to stick clauses which can't be enforced into contracts, assuming that nobody knows the actual law or can be bothered to investigate it. (In the Netherlands this position is especially silly, given that almost everyone has insurance which entitles them to legal representation.) Visit the legal aid society as well, once you've found something out, so that you're prepared if the landlord decides to fight you.