They're certainly not going to threaten England's involvement in the World Cup, that would be going to far so they took the symbolic stance of banning British Ministers and the Royal family from attending the games.
I read that the Brits already decided NOT to send any official representatives to the World Cup in Russia (Brits didn't qualify anyways, so pretty toothless).
I am more interested why they tried to Off him now, as he was living in the UK since 2010 under his own name.
Something must have come up that made him a threat.
There are repeated reports of Russia partially being successful in hacking into the Intelligence Networks of Western European countries.
Some maybe more aware of it than others, but Cyber-war is already in full swing.
Which offers the interesting theory that Russia recently got hold on what he actually told the West.