Here I will only talk of business masters, but NOT MBA's.

Coming from a country where getting 5 years of higher education (after your A levels)is strongly advised, it seems to me that, in the UK, not many undergraduates continue their studies with a masters'. It seems that many are just content with a 3 years' BSc. Now a few questions:

What is the rough proportion of business students that go on to do a masters'? (any website for that?)

Are my views on the UK "mentality" with regard to doing a masters and employment prospects justified?

masters are not that great unless they are tightly focused on the future job.
Companies rarely love you more (or pay you more) with a masters. Professional certification is usually better which is usually obtained on the job.