Hi Wau
I compiled quite a bit on Mr Copeland (related to my husband) & am in touch with other family who have more than I. I'll send you a personal message when I'm not typing on my phone in a few hours to see if I can assist. 
Hi, I am new to this site and have been going through some of my grandmother's papers.
She died in 1983 but I have only just recently acquired them.
I found some letters written to her by a Gertrude Ayton and the address on one of the letters is the Feldman's Theatre in Blackpool. The other two letters are not as old as the first one (dated 1976) which has an address in Blackpool.
After doing some research the Feldman's Theatre was opened in the early 1920's and was bought in late 1951 by Jimmy Brennan and the name was changed to the Queen's Theatre.
I have been trying to find out who this lady "Gertrude" was and I came across this forum on my searches.
I am convinced this lady is your Gertrude, as in the first letter she mentions being busy rehearsing for the Christmas show.
In the two later letters, she mentions...."I still see the Pro's, we are all firm friends"....and then goes on to mentioned three people, two of whom are quite well known.
I will be more than happy to let you have copies of these letters if you are interested.
I am not sure how the older letter will copy as she has written it in pencil, between rehearsals, and is quite hard to read.
Also, in one of the letters written in 1976 she says "I am expecting my eldest son and his wife sometime this month, they are going to take me back to Edinburgh with them for a wee holiday. Then in June I will have my younger son and his wife with me."
Tracey