Thanks abolabo
I did look there first and looking at it again two things come to mind.
One, where in that line would I put in my text string. e.g. "3-5 days" (i'm sorry my knowledge of all code is limited)
Two, that definition appears to be general to the whole royal mail extension. I need different delivery times for the different delivery methods royal mail provide.
In the six months I have been working of this I have learnt so much, but most of the time I am still in the dark. Though, I do have a functioning website, and even a few customers.
Thank you for all your help