Customer complaint escalation: CEO emails
If you need to go straight to the top with a customer complaint here is a website that lists email addresses for many UK companies.
There isn't a date on the site so it's hard to know how current some of the info is (not sure the Woolies one is still working....) but it may be a useful tool in any case. The site was last updated November 26, 2008 so the information should be current.
One would hope that the customer service reps at a company would happily and efficiently sort out your problems. The reality is this is the point most companies fall apart. Skipping straight over the CS rep and going straight to the top won't necessarily get you a reply from the CEO but their PA will likely read it and there's the possibility of it going on their radar.
As with any complaint keep your email or letter polite, reasoned and to the point. Ranting and threats rarely go down well when making complaints and you're probably better off structuring an argument that shows how hard you are trying to love them as a customer. This doesn't mean you should accept the excuses given though - be firm, know your rights and continue to fight your corner.