Transfer of Entitlement

I have worked for a company for nearly 10 years. 2 years ago there was a takeover and I was told my terms and conditions of employment would not change. I requested a new contract from my new employer but did not receive it. I subsequently went on maternity leave and was told my contract would be emailed but I never got it. A year later after I returned I was given a contract showing my start date being the date of the takeover and my original terms changed. When I told them I wouldn’t sign it without my service and my original terms I was told that that was an issue for the old employer. I firmly told them to look at this as my understanding was that this is their issue. Anyway to cut a long story short I still haven’t received a contract despite asking for it. The excuse is that they have not had time to redraft it!
I’m wondering if I should leave it alone or how long should I continue to keep requesting my contract for? It feels a bit petty at this stage and I cant understand the issue surrounding this.
I was the only person affected so there is no one else I can compare notes within the company.
Any comments or help would be appreciated