My family visits me all the time from the uk , for more than 6 weeks and have no problems . As long as he don't say he's coming to work ,or plans on staying here i see no problem .
It also depends what he is doing in Britain? Does he have a job? It looks like he does not (6 week off job?). Is he a student? It sounds better. He still has to have some funds (approximately $50x7 daysx6weeks=$2100).
If you wish to see how CBSA works at POE look at youtube- Border Security or Border Control