There would be a few red flags for me there. I've never yet had any form of survey where a valuation wasn't given.
Sure, there are always all sorts of recommended further actions/inspections - but always a valuation - so the buyer is playing games there.
On the other issue of the EA... I'm sure everyone's had stuff like this off agents... how did the buyer contact them initially without a telephone (number)? That's just well out of order - to not pressure the buyer for a number, huh!
But they've had a survey so they must be interested.
Have they given the EA their solicitor's details yet? Can the EA contact them that way? Can your solicitor?
If there's no phone number at this stage - exchange and completion could be nightmarish.
Personally, at the point where an EA has hacked me off so much that I have to visit in person to get the truth, then our relationship has already gone down the pan.
Frankly, if they wouldn't respond on the telephone, I wouldn't struggle not to lose my cool in person if they try and front me out and they will.
The best you'll get from them is an undertaking to send the buyer an email - because at this stage the buyer is more important to them than you are - as their commission is riding on this specific buyer - they would rather offend you than the buyer at this point - because they know you also don't want to lose the buyer.
Good luck - I wouldn't vist the EA in person unless you are a very calm person even when confronted with inaction.