This is called the Overton Window. It's typically the case for any system you are within, that the majority will consider the local "norm" to be moderate/centrist/etc.

Looking at international politics, or even (perhaps more relevantly) the history of UK politics, modern UK politics is extremely far right. Labour is a very good example (considered by many within the UK to be left). They have been right-wing since the "New Labour / Blairite" movement (verifiable either by comparing their policies to pre-Blair Labour, or to international socially democratic contemporaries). A similar example is the UK media coverage of Corbyn: his political views - which align very well with the Labour party historically & with international socially democratic parties - were portrayed as being communist/socialist. Corbyn's political ideologies never varied over the decades of his career, nor became more extremely left; rather modern UK discourse moved right, placing him left of the "new centre".