dwp caught out in lie re my PIP form

hi, first can I just warn everyone when sending forms etc back, to make sure you have them sent recorded delivery? I have a lifetime award of dla but received the dreaded pip form. First off it was dated 5th December and received around the 20th, saying I had 4 weeks from the date of the letter.!!! A friend called and I got a one month extension plus a further 3 day extension so I could get copies of relevant medical records. I sent the form back and paid extra for it to be signed for, and it arrived the day before the deadline. On Monday I received a letter saying they were stopping my dla as from 5th March as they had requested further information (which they hadn't) and I hadn't sent it in time. My friend called and was told they hadn't received my form until the 21st. She explained we had proof and they admitted there 'may' have been an error. She was put on to a case manager who said they would review the situation, but they could not guarantee to reinstate my dla in time. I had 3 days of total panic (I self harmed) before getting a letter that they would reconsider my claim and pay my dla until they have made a decision. AAAAAARGH!!!
How long do they usually take to make a decision? I'm panicking now because I have ADD and just read the report that 40% of people with ADD are refused PIP. I have ptsd and depression as well so maybe for once that's in my favour. I'm so stressed though.

I suppose its not really WHAT you have wrong with you....but how it affects you...and medical evidence confirmintg the issues you have always helps....