Britain is a fading power whose economy and population is going to fall relative to other countries over the next 50 years and no amount of chopping and changing governments is going to change that fact.
@anon_opin the population bit isn't correct, although it depends on which "other countries" you choose. If relative to Europe, particularly Western Europe - Italy, Portugal, Spain and Greece all have shrinking populations now and are projected to be around half of their 2017 levels by 2100, which will be a huge problem The UK peaks in 2063, later than Germany (2035) and France (2042), and by 2100 will be about 5 per cent lower than 2017.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30677-2/fulltext?dgcid=tlcom_infographic_gbd-population-20_lancet
Fading power though - yup!