I believe that under the Companies Act 2006 and Business Names Act 1985 every UK company should list on its website: its name; its company registration number; its place of registration; and its registered office address. I am trying to contact Sony Ericsson about a broken part on a bluetooth headset but can't find a contact address on the site. I'm not saying that it isn't there, merely that I can't find it.
Go to your local reference library. There should be several reference books which will give you the necessary information. Make sure it is the head Office address and not the Registered Office address. These can be different. You can also get the home addresses of the directors. You may have to pay a small fee for this info. I have done this for several companies.
I have found an address from Companies House. If I am buying online I always check that there is a landline number and a physical address, the latter being a legal requirementclick here. And I still can't find it on their website!