This is what Royal Mail has to say on the topic of posting to Russia:

http://www.royalmail.com/russian%2520federation

I found that link on Saturday but went to the Post Office today as promised to ask if there is anything else I should know.
The result -

• Express delivery to Russia is "temporarily suspended";
• All other services work as usual.

So it was a useful exercise. I have learned something new today. I did not even know there was an express delivery service to non-UK addresses.

So, to reiterate, Russia is still on the list. But of course, the final decision is on you. As of today (2014-01-27), I have only one "customer" and that is not from Russia