I know very little about escrow but I get the impression it is far from completely safe. I had most of my BTC stolen from an Armory wallet at the end of 2013. Then had BTC and huge amounts of altcoins that I mined lost through Cryptsy. I didn't find out until well after it has closed and 1 month after the lawsuit deadline
A few physical coins is all I have left and for my own sanity I cannot afford to lose them through a failure in the escrow process.
I am willing to let them go for 6.6 BTC for a face to face transaction if that helps with transportation costs.
There's no need to lose thousands of pounds because of your uncertainty on who to trust. There are some well established and very trustworthy people that can help you and a network of people that can ensure any trade to the USA would be water tight.
Monkeynuts for sure can help as he has dealt in Casascius coins for many years. You would be safe with his services. And I know he has the same trusted network that would make sure your coins would receive a safe journey. I use many of these people myself as a coin dealer at PhysiBit.
So, dont rush to lose money, check a few people out, you could gain
Viz