My wife has just been diagnosed with a ductal carcinoma, it'll either be an operation in a few weeks after some more tests, or 6 months of chemo and then the operation.
My wife has BUPA insurance with her employer, we've called them and the services they provide do sound good, however the NHS staff we've seen so far about this have all seemed excellent and appear to be moving things without delay (a far cry from the horrors of my 82 year old father's issues and NHS experience last year). I see one of the same NHS surgeons on the BUPA website as we saw at the NHS hospital yesterday.
I see that BUPA do pay you £100 per chemo session and and per operation if you choose not to use them (which sounds a bit low to me considering the money you're probably saving them).
There is a BUPA hospital that is about a half mile closer than the NHS hospital, has a shorter walk from the carpark, nicer decor, and free tea and coffee - but that's about it (as far as I can tell).
I see BUPA also offer at-home chemo, although it sounded like there were conditions to this (like not being able to get to the hospital).