No I mean what are the benefits of the UK to falsely claim it was Russia? There are none. Why its pretty clear why Russia would deny it. The West doesn't want to unite against Russia they want to do business with Russia. As shown proven by Germany/Western Europes and Russians extensive business ties especially when it comes to natural gas. And they're reluctant to agree to sanctions. The UK itself just bought a lot of natural gas from Russia. It's just that there are elements around Putin for whom it is so important to stay in power that they go to these measures.