I think you should widen your viewing to say -10%/+20%, of your budget, to help recognise fair value to when it comes to making a discounted offer, or not, of 300K. Just because you tell your agent your budget is say 350K does not mean you cannot offer 300K for a flat if you believe that is what it is worth. Also, explaining why your discounted offer is a fair offer is less likely to burn down bridges with an agent (in regard hot new flats coming onto mkt) than being perceived to just taking a punt.