You are not alone, everybody that plays League in the UK is having around 21-23 ping higher than normal, Riot is aware of the issue and apparently Virgin are now aware since a few hours ago (I'll take that with a grain of salt) I have however contacted a member of the team on the boards along with other people who are having the same issue and has stated several times that it is on Virgin Media's end and in relation to one of the servers in Amsterdam, where the EU West section of League's server is hosted (which is also where 98% of UK players connect)
He basically asks us to keep trying to contact Virgin to escalate the matter so they can contact Riot to both help fix this issue. But ideally they are looking to speak to the NOC department. Please look at the screenshots I have provided, and I hope we can all help to get this sorted as soon as possible, playing at 51-52 ping compared to my normal 29-30 is way too ridiculous and I cannot do it, so I am forced to stop playing online games until this issue is resolved.
We've got a few avenues we're chasing up here - Liberty Global as mentioned have requested MTR's which would be very helpful. Our Riot Direct team have also taken a look and believe there may be issues with how certain BGP prefixes are being advertised to us, so we're chasing that one down too.
We'll be keeping an eye over on the LoL boards on this, but if you can provide MTR's as requested that would be super helpful :-) Thanks for helping us push this issue!