If you think it's overpriced in comparison to other similar properties in the area then only offer what you believe it to be worth otherwise you could quickly find yourself in negative equity and stuck there when circumstances may require you to move again. Obviously you'd expect to pay a little more for something that's new if it's done to a high standard compared to similar square footage of a resale property but if you're doubting the value then chances are so would someone else when you come to sell. Depends how long you see yourself living there and the motivation for buying, an apartment is less for an investment other than being more savvy than renting but less about capital gain and more about being able to afford a life style of exterior maintenance not being your problem. If the economics are more important to you then lease hold is probably not right for you and you should consider a freehold house in a decent area even if it's not in great cosmetic condition.
As for telling the developers how much you love the property, absolutely not, they would not be ruled by their hearts and you shouldn't show your hand either. Telling them how much you've fallen for the place would be like telling a car salesman what your budget is, then they'll only show you something under that budget so you can't beat them down.