Santander limited edition easy access - 5.20% (for 12 months)...
https://www.santander.co.uk/personal/savings-and-investments/savings/easy-access-saver
Only available until 17th September, or sooner if it sells out.
Thanks for the heads up, I was with them anyway but only getting 4% so opened this and will move my money across.
I tried to get them just to change the rate on my account but they said it wasn't possible. Applied in the app for this new account and it was instantly available when I refreshed my app.