Going up such small amounts only works to piss the vendor off. Generally it's 5k steps at a time.
If it has everything you want then just take it. Mind you, with it only being on the market a week, the vendors will know you want it as you are bartering already.
Other option is put in a final offer of 211, then go quiet for a few weeks. See if they come back to you.
Also do some homework on local house prices and sale prices using Zoopla, and Rightmove.