Book those appointments early !

@June1952 - Can you ask to be put onto a cancellation list?  Sometimes it happens ....  
Mine's been to the same place too, (altho like you, my initial scan was local at the Breastscreen bus, then the biopsy was 1/2hr away at the closest town ... and every MG/US since then, is just under 2hrs away.)  

You are VERY lucky having yours with your Breast Surgeon & getting results same day @Afraser ....  My surgeon does an US when I see him every year, but not the mammogram.  I'm lucky that I've had the same specialist breast technician doing the US since 2018 each time and this year she did the MG as well  - but it is still up to 10+ days wait for the results .... grrr

@June1952
I agree, it’s good to go to the same place with all your records easily at hand. Not always possible of course. 

Yes, @arpie and @Afraser, they have a backlog due to COVID and people booking in who have not had them when they should.  Christmas was not mentioned at all.
My GP does the annual referral to the same place I've been to since diagnosis (well, after BreastScreen) which makes sense as it is the same machines and they have all previous scans to compare if needs be.  Have to have the paperwork or they won't make the appointment.  Timing is usually a couple of weeks ahead of the appointment but this year ....

My breast surgeon does mine at his facility - I hadn’t realised that it may be unusual to make your next appointment a year in advance, before you leave! I get my results before I leave too. I’ve never had one changed either. Clearly there’s been some dropping off (making or keeping) during COVID. But we’d all like them to be when due. 

That's a bugger, @June1952 - mine usually won't let you book in til 2 weeks before the 'review date' - but having said that - I've had all mine 'on time' even thru covid (and am regional as well ....) so have to travel to get the 3D/Tomo

Are you able to ring another centre & try & get in earlier - even make a trip of it - stay over night, get it done ...

I would email them (including the manager of the place) with a breakdown of WHY it is so important for you to have it done now - then they have a written copy of it, not just a 'he says/she says' ... 

I don't 'buy into' the 'it's xmas and it is difficult to get in' as NO-ONE is on holidays yet ..... are they trying to say that suddenly there is a massive RUSH on mammograms & US specifically at Xmas?  That's basically what I'd been told every year since 2017 when mine was first discovered (my Biopsy was between Xmas & New Year ...) The following year, they found another funny bit & the biopsy was on Xmas Eve!!  So then I moved my yearly exam forward to October (the Onc was happy to do the referral with that date) .... and it has been a bit smoother since ...

Good luck. xx