Changing anything other than your postcode will make little difference.
JuJuuk68’s summary is correct and combined with the insurers inability to cover premium to cost deficits in the markets results in the premiums taka is quoted.
The only way to get it substantially cheaper would be if you find some one incorrectly rating the risk.
Its not really the insurers fault they merely do the sums, politicians make the choices that shape society.
Get a bike for a year or two, it’ll keep you fit!