It's a bit "one weird trick", but you're right that absolutely the best way to get consumer problems addressed in the UK is to use the word "complaint". It star

It's a bit "one weird trick", but you're right that absolutely the best way to get consumer problems addressed in the UK is to use the word "complaint". It starts the clock as complaints typically have to be addressed within certain time limits. If you don't use the word complaint then companies can argue that they thought you were merely providing feedback or engaging in something other than a complaint. As soon as you use the word complaint, they can't argue that and it puts you on track to escalate to the ombudsman and the companies know it, and they know you know it.