you have more than enough room to alleviate overcrowding in Britain if the will was there to do so,

No we do not Jim.
Wiki.
"The official figures[6] from the Department for Communities and Local Government for England (not including the rest of the UK) are that on average 498 people sleep rough each night, with 248 of those in London. There are a total of 84,900 households (which may contain more than one person) that are classified as homeless"

There are not 84 900 spare houses.
And we have 470 000 EXTRA people every year.

If you deny that England has a severe housing shortage and desperate homelessness, you are an ignorant fool.
If you do not deny it, where will you put even more people?