What are the reasons for our poor housing options, homelessness etc ?
Off the top of my head, very quickly I would say: 'right to buy', non existent social housing, the fact that we build a small amount of 'affordable' rather than 'social' housing, the number of people with second homes, and the ridiculous renting/private landlord situation in this country, build to rent, short tenancies, affordability of rent, the number empty homes in this country. All of these probably have a much bigger impact on housing in this country than asylum seekers. (For example, the end of private tenancy is the leading reason for homelessness in England).
Speaking of homelessness, the on-the-street homeless people I work with all there because they can't get a place in a shelter/hostel (there usually are places, but they're not allowed in). There are for various reasons but the most common are being banned for drink/drug use, a history of violent/criminal/sexual behaviours which make them too risky to take again, mental health problems (ex-military with untreated ptsd etc). If there were adequate services to support these issues, homelessness in this country would look very different.