Actually the British Embassy website redirects you to the UKVisa Site when you click on 'Apply now' anyway, and you should at some point end up here:
http://www.visa4uk.fco.gov.uk/ApplyNow.aspxUnlike the US system, you don't really need to know the names of the forms your filling out etc. You just tick the boxes that are relavent to you, and the online form adjusts accordingly.
When I did it in July, at the end of the form, you are asked if you want to file your evidence papers by mail or in person. And also pay now or later. I recommend that you choose pay later. That way if you see any mistakes on your form you can just submit another one. Then only reference the correct application number with the evidence that you send in, or when you go in person to give in your evidence.
The one thing about the UK application that is harder than the US one, is that they aren't as specific about the evidence that they require from you. I think it's worth checking out the many forums dedicated to moving to the UK, to get peoples personal accounts of the evidence you send in. One of the major things is that they not only look for 'something' with both of your names on it as proof of your relationship, but a number of things from a variety of sources.
best of luck xxx