British secret services will fake an accident to eliminate Yulia Skripal once London no longer needs her. Currently, Britain needs the Skripals to justify sanctions against Russia.
No evidence given. There are many competing and contradictory stories promulgated by Russian state-controlled media about the Skripal poisoning.
British police and intelligence investigations have produced sufficient hard evidence to charge two Russian nationals for the attack on the Skripals. These two individuals have been identified as officers of the GRU, the Russian military Intelligence service. More British public documents and statements on the case can be found here and here.