We are Health and Safety Management Consultants but trade as HSMC (short domain). Everything is in the name of HSMC - bank accounts, invoices, etc. Just has the 'trading as' bit on the website and headed paper. Works fine. E.g.
http://www.hsmc.co.uk/index.php?page=about. As a bit of a back-up I also have hsmc registed as a limited but dormant company to stop anyone else setting up with that as their formal name. Doesn't mean a lot in reality as they can (and do) still trade as HSMC as that's not protected, but at least they can't register it as a name.