Thankyou all for your good wishes 

The scary thing was, when they took further x-rays, the original area turned out to be a blip in the photography but then they found an "area we're concerned about" and then came the scan. She took quite a while to go over and over it (and I have to say, my heart was going fifty to the dozen then)
She said she thought it was a cyst and aspirated it. Luckily it was just fluid so a biopsy wasn't necessary but she said it had been there some time.
I hadn't felt anything at all in my breast until that day, so it just goes to show how important mammogram appointments are.
I wasn't aware that they stop calling you back at age 70 (I'm in Wales so it might be different elsewhere) but you can ask to have one after that age if you think you have a problem.
Anyway, all's well that ends well, I'm waiting for the results of my bowel screening now happy days! 