Denied entry to UK and sent back to US – mistake?

I met my boyfriend a year and a half ago while studying abroad, I think came back to the UK and we spent 6/7 months in a long distance relationship. In January this year he came to the UK on a student visa which ran out in June at which point he went back to the US to apply for a summer postgraduate visa which would allow him to work here during the summer (before he begins the second year of his course in September). Despite having proof from well known companies of an internship, proof of funds, proof of school etc. he was denied the visa but on a basis that must have been a mistake (his University is not accredited – it ism the University of Sussex). The appeals process takes months so he decided rather than not see each other all summer he would come here anyway on a tourist visa and apply for his student visa (whcih would start in September) while he was here – because he has checked with home office and they confirmed he could do that. On that basis he arrived in the UK this morning with a return flight in December – longer than a normal tourist stay would allow but as he would be restarting University in September, he would only actually be staying as a tourist for 2 months or so. They told him he wasnt allowed to apply for his student visa here but had to do it in America and based on that his flight booking involved overstaying his welcome. He offered to change the return ticket to a month from now – a tourist period he would be allowed but the refused saying his original intention had been otherwise and he is now sitting on a place back to the US and I am devestated. Any previous experience of something like this? Suggestions? Thank you.
If he now applies for his student visa and gets it, can he for example enter the UK as a tourist in the next few weeks with a return flight for christmas but also an outbound flight somewhere other than the US after a month or so (say we go on holiday or something) then return to england activating his student visa after the 2 week or so holiday?

They are very strict about not ever allowing a visa transfer from tourist to student. There was no way that your boyfriend could have changed his status whilst in the UK so I cannot imagine how he thought he could. All the university websites have a warning about never attempting this.

He will have to be patient through the appeals process. If refusing him the student visa was an honest error he should be ok. Hopefully they will not pick up the deportation.

Edit: on no account should he attempt to enter the UK now except on his student visa. He could find himself permanently barred if he does this.