I don't know what a V5 is, but it sounds like Tony P and Colebatch are all over it.

For US riders, I have entered Russia many times using my title, rather than registration. This works fine: while they always ask why the license plate number is not on it, are are satisfied by the response that "that's just how they do it in Washngton." Also, I usually use a color photocopy on thick paper, although at least once a guy at the Ukrainian border spent about twenty minutes looking at it under some kind of infrared lamp or something, I guess looking for watermarks, etc. He was rather suspicious, but let me through. I always bring my original as well, but don't like to use it.

When you plan on using documents translated into Russian, I highly recommend getting them apostilled, rather than just notarized--the point is that the Russians have no idea what a British notarization looks like--it could just as well be from the local pub, as Tony says--and the apostille is an international certification that yes, this document has been properly notarized in the country where it originated. You might be able to get by with just a signed Russian version with a couple of random stamps on it, but I wouldn't want to take the chance. Even if someone you know has done it, the guy at the next border post might have different ideas.