https://www.gov.uk/british-citizenship
You can usually apply for ILR after you’ve lived in the UK for 5 years.
To apply for citizenship with ILR you must usually have lived in the UK for 12 months after getting it.
但重點係你呢個離英1.5年假設係break咗呢兩條rule
1. spent more than 450 days outside the UK during the 5 years before your application
2. spent more than 90 days outside the UK in the last 12 month
所以呢個假設係多舊魚
有錯請指正