I am a Tier 4 student in the UK and my visa will expire in late Jan 2019. I have given notice in the local council for my marriage with my girlfriend (she's a Tier 4 student as well and her visa expires in late Jan 2020). I have received the letter from HO that they will extend the notice period for another 70 days.
The question is that in 70 days my visa will expire ( for more than 28 days). Shall I stay in the UK as an overstayer waiting for the interview/investigation of HO, or, shall I go back to my country and apply for a visitor visa and come back to the UK for the HO investigation (and then get married)?
Many Thanks


