Barclays pays 5.00% monthly on balance Up to £5k, equal to AER 5.2% in the rainy day saver account.
Account available to blue rewards and premier account holders.

Chip easy access is 5% no more than 3 withdrawals a year otherwise it falls
If you can find someone to give you a code they will give you a 0.26% bonus for 90 days.

They're most useful for the target customer: people who have a small amount of cash spare each month and want to earn a bit of interest. Less useful for lump sums or larger amounts. John seems to do a spot of CC stoozing to max his returns.

The T&Cs are all different: most have variable rates, and many don't allow withdrawals before the term or have restrictions. Some allow as little as £50 pm max, but I have seen up to £1000 a month in the past. You can pay them by standing order, which could mean having money sitting in a current account earning zilch for a bit. With Chase you can pay standing orders from their savings accounts.

The best payers often require a current account to be opened and several offer EA accounts with better rates for current account customers, eg Santander has an easy access account wiith faster payments etc paying 7% on up to £4k.

You also have to be realistic about how much you gain. For the 7% Yorkshire RS the max you can pay in is £50 pm, so you could have £600 at the end of a year, but the average balance you have would be just over £300. So £300 x 7% = £21 interest.

So very good for the target customer with a spare £50 each month but perhaps not so good for someone with a lump sum. They could put their £600 in an ordinary easy access account and get 5%, e.g. Santander Sunny Day, or a blended rate of 6% using the RS + EA saver.

That would give them 1% or £6.00 more for their trouble than just having the whole amount in the EA account where they wouldn't t be limited to £600. Or they could use a 1 year fixed rate account. I got a 5.40% 1 year fix last month and Ulster Bank (a trading name of Natwest Group) currently have a 5.2% EA for £5k+ reducing to 4.75% from 10 October.

Have a peak at the MSE board, there are people there juggling a dozen or more accounts, carefully timing payments, and seem to enjoy it as a hobby. I get quite enough fun paying my council tax bill each month. Horses for courses, as they say.

I can't be arsed with all this chasing interested rates up and down the high street. I have our £15K emergency fund in a cash ISA earning 2.65% but wouldn't care if it was earning zero interest.

The bulk of our retirement cash buffer is being accumulated via salary sacrifice inside my pension, around £80K so far earning 5% BOE base rate with no AMC.

I have £8,500 NatWest 19 months zero interest zero fee.
And I have just taken out ANOTHER! NatWest £8,750 13 month zero interest zero fee credit card.
They are getting harder to find. I often find going direct can turn up some very good deals.
Wary of fees as a 3% fee on 1year balance transfer is equal to 6% interest.
IE front loaded Mafia interest rates (literally).