PIP award ending before assessment

My current PIP award is due to end at the beginning of March. The review form for some reason wasn’t sent in March as I expected but in August, I needed an extension to complete the form but returned it within several days of the extension date. DWP received it on 21 Oct, they decided to send it to ATOS for an assessment who received it on 21 November. I found this out when I enquired about the progress on 21 January and DWP advised me to ring ATOS to see if they could carry out a paper based assessment. ATOS considered this on the same day though I didn’t get the letter until a week later, 27 Jan when they said they’d decided I still needed to have a home assessment (I’m don’t understand why given my situation has not changed but got worse due to other diagnoses. My review form included evidence to support this). During the phone call with ATOS on 21Jan when I expressed concern that my award was due to end soon I was told they were still within their contract agreement for an assessment to take place . Yesterday I rang to check progress and was told there was no guarantee the assessment will take place before my award ends. I asked why it was taking so long and why I should be punished for them not having enough staff. They said somebody will ring back in 48 hours. In the meantime I’m putting together a letter to send to DWP and my MP (not sure it the latter is allowed to help anymore). Has anybody else been through this? What did you do and what was the outcome?