Cancelling Medical assesment

Hi.
I'm seriously preempting here.
But I have some alternative medical treatments booked in Germany ( ozone, vitamin C infusions , photon therapy etc)...All highly effective but not recognised by the NHS/British medical professionals
My question is, the trip is booked within a month of putting in my questtionairre, and I'm worried I might be called in to have a medical whilst I'm away.
What's the protocol for rescheduling if I need to?
Is it even advisable?
I don't really want to mention Germany as they might hold the fact that I can get there (albeit with assistance) against me .
Fingers crossed all the timings work out perfectly , or god willing I won't even be asked to assessment and therefore won't need this advice, but just to put my mind at rest ( otherwise it'll be playing on my mind for the next month)......Opinions are welcome.
Thanks.

do you have anyone who can open your post while you are away?
I told them of dates i was unable to make & the computer gave me said date.
When i called to rearrange the woman was lovely, just doing her job, saying she could spot the error.....
if you have someone checking your post, just give them a call to rearrange for a date when you will be home.
Good luck with all your treatment... Heard wonderful things re Ozone n Vit C