I am divorced and want to protect myself should the current amicable relationship change. I invested £60,000 as a deposit on our family house which is now rented to tenants. The property is in my ex-wife's name, although the solicitor did draw something up confirming that I was involved to the property - I can't remember what form we signed. How do I find out & do I need to lodge another form to stop any transaction from happening without my knowledge?

YES, you need to lodge an ESTOPPEL
Notice to the REGISTRAR of Properties.
You should get the DEED noted.