Unable to send by Recorded Delivery

You'll love this (not) and I think it needs passing on. I had some extra info that I needed to send in before my PIP assessment and was given one of these new Freepost addresses. When I went to the Post Office they REFUSED to allow me to send it Recorded as there was no Post Code! Quite adamant that without a Post Code Recorded Delivery (or Signed For) was not accepted. Got a bit nasty and told me to contact Royal Mail - as if that would do any good! So I have sent my stuff off (copies fortunately) with no proof that it will be received. Were you aware of this previously please, and if so any suggestions? I am thinking of sending off again but don't know who to address it to.

Hi, I'm just jumping on here years later. This conversation came up on a Google search I just done

I recently requested a mandatory reconsideration for my Universal Credit WCA. I had a lot of extra evidence to send, and was told to use the address
"Freepost Universal Credit Northern Ireland"

So because there's no postcode, Royal Mail couldn't send via recorded delivery

I rang to see if there's an alternative address. Apparently not!!! They couldn't tell me what the postcode is of this mystery location!
My only other option was to upload every single page onto my Universal Credit journal, or take it to local Jobs & Benefits office for them to scan it.
Neither option suitable, I had 100 odd pages. Also don't feel comfortable that my work coach could see all my personal details & medical issues.

Anyway, sorry, just pointing this out incase it's of any use.