Ask for them in a bag with no air in at the tackle shop, stick them in the fridge then when you get on the bank, open them up and stick them in water straight away.
I've found frozen to be ok, but Ive had some I've defrosted, frozen, defrosted and then used.....they were absolutley manky but the fish loved them!
"Fresh" is best IMHO and dont neglect other colours not just reds too.
You can do the same with pinkies.