recording ESA medical / changing the appointment

I received a letter with an appointment date for my ESA (re-assestment) medical just 1 week after I sent the forms.and the appointment is in less than 2 weeks.
I wasn't expecting it so soon after I sent the forms.

I'm not really prepared for the face to face assessment and prefer to delay it if possible.and also like to record it.

I've read the guide, but my question is how long notice should I give them when I write a letter requesting recording?
is sending the letter 1 week before the medical enough? or should I just telephone them instead?
what will happen if I send them a letter? will they send followup letters? because I don't think there is enough time?

also is it possible to request a change of appointment and do I need to provide specific reason for that? and when and how should I request that?

I will email them but since emails could be missed, is it a good idea to phone them as well and also post a letter too?
which address should I post the letter to? the address on the website or the address of the centre on the appointment letter they send me?

also what should i expect after this? will they contact me before the appointment regarding this request?

thank you.

When you send a letter send it recorded delivery and keep it safe or they will just deny they received it, also it shows your leaving nothing to chance.

I would do what Gordon said, do all 3 then your well covered but only if you can prove it.

Good Luck

I will do all the 3.
and I will send is via recorder delivery too.
the problem is my assessment is in around a week.
so what will happen now?
do they send an acknowledge letter? or will they contact me?
how do I know they have received my request and whether or not they will provide recording option?