Take your own medicine, .Gov...
Given that almost all public sector Web sites aren't compliant with RFC2822, it's about time a few more Goverment systems were Open Source.
Try entering an e-mail address containing an ampersand ("&") in the local part into any Government Web site, and see what I mean ("Please enter a valid e-mail address"). Of course, the restriction comes about because the proprietary "GovTalk" ( a bastardised version of Microsoft's BizTalk) has to block the ampersand character in input strings, because of Microsoft's horribly broken security - their software is particularly vulnerable to strings containing this character.
The B&Q Web site is the same, a bit embarrassingly for them. But of course it's a perfectly legal character as far as the (open) IETF standard RFC2822 is concerned. It's funny, corresponding with Government departments that tell you it can't be used in an e-mail address, when... errmmmm... they're emailing you using your e-mail address with an ampersand in it... :-)