Do hope your sale goes through without problems. Surely, measuring up really only takes place right towards end of selling process, when idea of moving date is in sight.
Bad practice by EA. When I moved to this flat three years back, I asked to have a quick visit to measure up three weeks prior to what actually became the moving date. I also needed to be able to make a 'map' for my daughter who was going to be the person who got the keys and let in the removal firm whilst I was still driving down here.
The flat was virtually empty, just last few bits of furniture as the previous owners had died, yet the EA came and sat in the flat whilst daughter and myself did all that measuring/mapping, etc. as I expected.
Recently, as Secretary to the Management Company, I let someone doing a quote for carpet cleaning into an empty flat soon going on the market. (The current probate owner live a long way away). Would not have dreamt of just giving this company the key - I opened up, sat in there whilst they measured, etc. and locked up when they left.