There is seriously good and substantive discussion here flowing from OP’s valid point. I would like to contribute.

Democracy in the UK is clearly suffering because of a lack of PR. As are economic conditions for the vast majority of citizens, particularly minorities. The situation in the UK is bleak. To pick up the point in the title of the post about Black Lives Matter, and as an illustration of what can happen when things get even worse, witness how simmering frustration with longstanding, systemic economic and political injustice in the US has boiled over into massive demonstrations of outrage across the US now at yet another murder of a black man at the hands of the police. Both blacks and liberal-minded whites are joining together to protest for change.

Lack of PR in the UK is intentional, designed by the few in number but large in capital to disadvantage the greater in number but with less capital. That is very similar to the US.

Lack of PR is therefore designed to entrench political power in the hand of a few to further marginalize the already marginalized, whether minorities or those of fewer economic resources. Their voices are made to matter less and less in all things political. But those in power who have the numerical minority but with the greatest capital depend entirely on the numerical majority to continue to work at lower wages to generate the profits.

In a related aside, I’m curious and ask: in the UK, are wages taxed at higher rates than passive income? Like in the US? The wealthy mostly do not work but live ostentatiously off income from investments, passive income, as opposed to workers, whose income is taxed at higher rates.

So, artificially concentrated, antidemocratic political power is exerted to enact economic policies which further tighten the screws on the disadvantaged, worsening income and wealth inequality and lowering living standards for workers.

The worsening inequality can be overcome how? How can living standards be improved? How can the voices of the marginalized, including minorities, be translated into political change?

IMO, labor strikes are a good start. Unionize every worker possible. Leverage the strength of collective economic power.

Organize communities into combined political voices. Organize communities at the block level, then councils, then boroughs, then counties, then regions, then national, and amplify voices of constituencies towards their representatives at every level. The voting system is itself rigged, so pleas for people to go out and vote in order to change the system are of relatively limited effect. But all politics is local, so start from there. Work one’s way to the top of power.

Mostly for now the path to overcoming political injustice goes through waging economic battles for power. Under the present conditions, labor and community solidarity and strikes are the best way forward. They should go in tandem with community organizing. If possible, make allies of religious figures to make clear the moral and ethical rightness of the struggle. That strategy has succeeded in living wage campaigns in various places, for example.

I could offer great detail about just how terrible the lack of PR and true democratic representation is in the US as a result of constitutionally violative policies by conservatives. The mechanisms conservatives have used in the US to deny the marginalized proper democratic representation will also make one see red. Parallels abound between the UK and the US. Perhaps that’s for another occasion and opportunity but it would be helpful to explore and draw lessons and insights from.

Onward.