Thank you everyone for your support and advice. I appreciate it. And @Keeping_positive1 I'm so sorry you had such a dreadful time with those delays. That should not be happening these days.
I saw my GP today and got a copy of the report which specifically states "/Hospital/ has been contacted however have stated no previous imaging available for patient".
The upshot of this is that the report cannot definitively give me a result without comparison to previous scans. It says there is fibrocystic change but until a previous scan can be found, they can't say whether this is a normal part of me or something that needs further investigation. So I have to wait for a follow up report.
I've looked at the US scan pictures and they've marked up a very definitive black spot.
So now that I'm armed with this little nugget of information, I'll be asking some very pointed questions at my follow up at the Clinic on Monday. If they cannot offer any satisfactory explanation, I'll be requesting information on how to make a formal complaint.