Transferwise

Following James' recommendation, I have used Transferwise regularly for the last 6months have have found them to be excellent, and, with best rates of exchange

I have also used Transferwise for small transfers from UK £ to € and been very impressed with speed and rates. I now have a much, much larger sum to transfer in the opposite direction € to £. I wonder what security there is in transferring €000,000's? Exchange rate is one thing, total security albeit at a worse exchange rate is another. Has anyone done a €100,000's transfer. Do I have, should I have more confidence now M Branson is backing them?