The seems to be 2 possible trials looking at 2 different types of cancer one in Oxford for bone cancer and one in London for rectal/pelvic cancer

Oxford has been running for some years and the London one is a phase 1 or 2 trial, I don't know much about this treatment or its effectiveness but you would need to contact the trial co-ordinator and see if you mum was eligible for the trial you have in mind and what the cost might be if the is one, given the current state of things in the UK.

Both are hospitals that run trials and I know of them because of lymphoma and the work they have done, but thats the limit of my knowledge.