I'm using powergen for my gas and electricity at the moment (though this will change as their tariff is not really green enough, they don't retain enough green certificates)
I sent them this email:
I previously wrote to you regarding your rather annoying 'browser detection' script - and its blocking of the Firefox browser.
I have yet to receive a response. However I have installed a plugin to fool your site into thinking I am using Internet Explorer, when in fact I am not. The site works without problem when this is done. I am sending you this message so that when you look at your logs you will not assume that there is nobody using firefox. Indeed, I imagine that others will simply use the plugin without informing you.
Please amend your script, it does little except annoy.
Migrating to Firefox is a great idea. I've not looked back, and now I've got the user agent extension to fool brain dead websites (I only enable it when I have to), I find that I only run MSIE to check that there are no major bugs when MSIE mis-renders my websites. (e.g. MSIE mishandles .png graphics, but I've decided to stick two fingers at microsoft on this one - as it's not a fatal error).