I have never held a passport I came on my mother's passport and it's stamped her and 3 children Indefinite leave to remain without restrictions. I have done schooling and work but now most jobs ask for proof birth certificate or passport. I don't possess any.

I was born in Bombay 1975 and entered UK in 1979 on my mother's passport which is stamped IDL no restrictions.
I don't have a birth certificate as I never had one and my parents have passed away.
I have lived in the UK for 39 years with no problems but cannot travel. Any advice please.