MR advice?

So relieved to finally get my MR sent off last Friday. I attached your very helpful covering letter and covered the descriptors. I enclosed a copy of my Independent Assessment complaint as Dwp suggested along with a copy of my care plan and an up to date supporting letter from my psychiatrist. I posted them recorded delivery and can see it has been delivered and signed for. Should I assume they have received it or would you call to clarify? The 4 wks deadline was from the letter dated 2nd September.