I raised an HR case last year and had the following responses:
Please be informed that there is no change in the redundancy terms for the employees those who all hired before 01 September 2018. The new UK redundancy policy is only for the employees who all are hired post 01 September 2018. I have attached your terms and condition document for your reference.
There were two documents, one for ex CSC people for prior to the new company and one for ex HPE people prior to the new company. Your conditions should be those that were applicable to legacy CSC employees. You can ask HR for a copy of those conditions.
Keep copies of emails that you get from HR in the event of any legal challenge you might have to make. I have kept copies of everything in the event of having to go to a tribunal.