Within member states of the EU) the phrase "third country nationals" (TCN) is used to refer to non-EU nationals while in a EU member state.
Terms to use for subject searches in SOLO:
Political refugees -- Civil rights
Immigrants -- Civil rights
Refugees -- Civil rights
Aliens -- Civil rights
Subject searches to try in SOLO:
Deportation -- Great Britain
Emigration and immigration law -- Great Britain
The Official Papers collection on Floor 0 of the Law Library will have a lot of material for researching the development of UK government policy over the years.
Various charities seek to improve the lot of non-citizens in the UK.
Some are linked (in alphabetical order) below:
Hate crimes in UK are "Crimes committed against someone because of their disability, gender-identity, race, religion or belief, or sexual orientation are hate crimes and should be reported to the police.
Hate crimes can include: threatening behaviour, assault, robbery, damage to property, inciting others to commit hate crimes, harassment "