We own a holiday cottage which we let out, and to be honest would be upset if we weren't told that you were struggling with the oven. To tell you that it takes 'guesswork' is unacceptable, so I would suggest a brief email to either the agent or owner (depending on whether you booked direct), and explain that you're struggling with the oven, and ask them to come and rectify it a.s.a.p. I note that you don't state what type of oven it is, gas? electric? If it's gas, then safety could be a problem, so tell them that you are worried for your safety, and then if they don't get it fixed within 24 hours, or give a reasonable explanation as to why they can't get it fixed that quickly, then you should ask for a refund, suggesting an amount which would make you feel adequately compensated. Most holiday cottage owners are only too happy to help, although in this case, it does sound like they don't really care about the property and its contents, in which case I'm afraid the best advice I can give, is to get on and enjoy your holiday, eat out if you can afford to, and if not, try and make the best of it with the facilities that you do have, then upon your return home, write them another email, expressing your displeasure that they haven't rectified the problem during your holiday, and again request an adequate refund, pointing out that you feel sure that they wouldn't want the bad publicity, should the matter not be settled to your satisfaction. However, PLEASE don't let this spoil your holiday. Good luck.