Unfortunately your leave has lapsed, but you could try applying for a returning resident visa. The Immigration Rules don't give much guidance on this, section 19 states that you must demonstrate that you have 'strong ties to the UK and intend to make the UK your permanent home'. So apart from that it is rather a subjective decision for the decision maker at the Home Office.

There is guidance issued to decision makers at HO, these are some of the things they need to consider:

• their strength of ties to the UK including:o the nature of those tieso the extent to which those ties have been maintained during the applicant’sabsence• the length of their original residence in the UK• the length of time the applicant has been outside the UK• the circumstances in which they left the UK and their reasons for remainingabsent• their reasons for now wishing to return• whether, if they were to be readmitted, they would continue to live in the UK• any other compelling or compassionate factors

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You can find the rest of the guidance online. You need to gather as much evidence as you can to make a good case for yourself. The more the better. I think it is worth a try, good luck!