I personally wouldn't tie up savings for 7 yrs, on a return of 3.5% but if you have no need for these funds and have other monies available in instance access for emergencies then it's not a problem. The down side with tying up is that interest rates will rise and you'll be left behind with a lower return.
123 current account with Santander offers 3% up to £20000 and Lloyds current accounts 3% up to £5000 and you can have three accounts.
Both are current accounts so easy access and you receive the interest monthly.
Moving money to get the best rates is a must, the banks love people who leave there money for years in low paying accounts because they can't be bothered to switch accounts. I have no such problem.