Hi there
In the current climate, anyone who ignores a buyer in this manner is not worth dealing with.
The real question here is how badly do you want this particular property ?
Only you can answer this, but you should certainly ask yourself this question before you deal further with these jokers.
You've made a second offer after the first was rejected, so maybe you'll make a third ? and a fourth ?
As long as you are contactable (you are sure the estate agent has your contact details), then I would not make any more contact with these individuals. I would not write letters to vendor's etc. It is not your role in all this to educate anybody.
I do fully realise that what I have said is totally without attachment for this property and is made from a totally uninformed position;
BUT when dealing with estate agents, builders, etc. they should be treated with the same level of contempt they have shown to you.
T