A 'gymslip mum' is a teenage mother. A gymslip is a sleeveless dress worn over a blouse as a school uniform, also known as a Pinafore dress in the UK. They are sometimes referred to as a "jumper" in the US. More commonly, they are called "overalls" because the shoulder straps may closely resemble those found on denim overalls.
Nell Hudson (Paulette Roland) and Maria Doyle Kennedy (Attracta) both have starred on Outlander (2014). Hudson played the character Laoghaire Mackenzie and Kennedy played Aunt Jocasta.
Linda Bassett (Nurse Phyllis Crane) and Matilda Ziegler (Dulcie Roland) also worked together on Lark Rise to Candleford (2008) as Queenie Warner and Pearl Pratt respectively.