Find Ancestors

Hi everyone I have a right mixed bag of a family tree to try and trace , my dad was adopted at 6 weeks old and is now 73 he along with my mum traced his birth family in 2000 but sadly missed his mum by 7 years. His adoptive name is O'Farrell and lived in Aberdeen and we can not find out any information on this side of the family at all all i know is they lived at Park Street Aberdeen in 1934 and his adoptive parents were Robert Scott O'Farrell and his wife Sophia O'Farrell nee Thomson. His birth family are the Conn family from the Invururie area i have found the Conn family history on Scottish people and makes very good reading, but this is where i find it weird there is loads of information on the family going backwards from the 1800's but can not seem to find anything forwards of that especially into the 1900's. My mums side of the family is the Jacobs from the Lambeth area, my Grandad Henry Charles Jacobs was born 7 July 1899 to Eliza Ann Jacobs, i have had trouble tracing grandads side of the family any further back than that, there is a question as to the family being of Jewish descent but not sure. My mums mum Louisa Rose Terrell was born 1 August 1901 or 1910 not quiet sure, with a lot of help from other members on different sites i have managed to find that nan's side of the family originate from Devon/Cornwall and have managed to trace back as far as my great great grandfather Henry Terrell born in Tavistock and was a carpenter. This is where i have come to a stand still and dont know where to go now, any help or advice from anyone would be greatly appreciated i am open to any help anyone can give me, Many thanks for taking the time to read this and i look forward to being a member of this site. Dee