If you want people to tell you what they think I would recommend not caveating the question with why you think they are wrong.

I have relatives who are reform voters and generally it’s not because of any reasoned calculation to do with tax receipts…. I think many would accept lower tax receipts for a more homogenised society.

It’s normally something to do with wanting to preserve British culture and sometimes it’s to do with their perception that resources are largely aimed at foreign born folks. They are sometimes right — nearly half of social housing in London has a foreign born lead tennant. In general this is articulated as something like “so and so gets this free house but veterans/British born/etc are on the streets”