davidmc:apparently as I have only transferred from one Santander-owned bank to another, the 12-month rule applies and I will not get 6% on my Abbey current account balance. I suppose it is right,
I have no idea whether you are right to suppose or not but a brief look at the offer page and account terms & conditions doesn't immediately support the Abbey claim. How do you suppose they are right?
To answer your question differently, is it wise to have up to £2500 in a current account just to receive 6%? No, because such easily accessible money is more vulnerable to fraud. Far better to have the "free" overdraft account because fraud on debit balances is limited to £50.
Alternatively look at the HBOS rewards current account offer.