My mum went to Holt Hill in the 50`s. There are some good pics and history of it in Ian Boumphreys book, A Pictorial History of Birkenhead. An excellent read and reference book, my beloved bought me for my birthday, ex Birkenhead Library!!
If anyone is interested in the history of Holt Hill Convent, I now have a 'mini' website here. It's a bit small at the moment, but hopefully it will grow in time.