https://www.gov.uk/tier-2-general/switch-to-this-visa
http://www.admin.ox.ac.uk/personnel/permits/status/
Only the following may apply to switch into Tier 2 (General) employment without leaving the UK:
Tier 1 migrant;
Tier 4 migrant;
student;
dependant partners of student visa holders;
student nurse, but only if your certificate of sponsorship shows that you are being sponsored to work as a nurse, doctor, or dentist;
student re-sitting an examination;
person writing up a thesis;
overseas qualified nurse or midwife;
postgraduate doctor or dentist, but only if your certificate of sponsorship shows that you have been sponsored to work as a nurse, doctor or dentist;
student union sabbatical officer;
qualifying work permit holder;
Highly Skilled Migrant;
a participant in the International Graduate Scheme (formerly known as the Science and Engineering Graduate Scheme);
If the migrant is not in any of these categories, they must leave the United Kingdom and make a new visa application at their local entry clearance post in their resident country.
回国 = RLMT + 名额