Think Revolut limits the amount you can change in one go and there’s a monthly user limit too and I’m pretty certain your size would breach that.
I mainly use CurrencyFair but I have also used Wise and both are similar. You’ll pay approx 0.5 cent or less away from the market rate. The advantage of these sites is that you can break your order into smaller pieces and use limit orders to trade. Normally I’d suggest you spread something like this over 5-10 transactions to smooth your FX rate but GBP is at a relative weak point vs EUR on a longer term chart so it’s not a bad time to buy GBP but it can always go lower (!).
Also, when your account is open test it with a modest amount to check everything thing works and always transact during normal market / business hours.
Updated July 2014 The best way to do this is to use one of the money exchange services as they give rates better than the banks. (However, Chillaxed is getting better rates from Bank of Ireland on large regular transactions, around $500,000 a year) You can ring around a few of them and open...