Ok so this requires a huge POD, but bare with me. After the Second World War, the UK government actively invited workers from the colonies and parts of the empire to come and work in Britain, effectively kick starting the modern multiculturalism we see today in the UK. They did this because we simply did not have the required work force in the industrial sector. What if they did not do this, how would society look? What would the British economy look like without that labour? Obviously a serious slump would occur back then. Would policies similar to Thatchers be introduced sooner, or possibly never at all?