I am with Santander and most people complain about them and to be honest I have had a bit of trouble with them in the past.
Anyway last week without notice their online banking was completely down and my card kept on getting declined for no reason,
Sent them a email complaining. They have replied saying they were at fault and have gave me £35 as a gesture of goodwill.
Quite surprised as I expected about £10 most for the trouble they caused me :)