Thanks.
Is there any formal way of me declaring I do not have any beneficial entitlement to the property?
When I buy my property (in a few weeks) is there any steps for me to undertake?
Your new property transaction is completely unrelated. The only thing I can think of that you might be referring to is the mortgage - but your new mortgage, if you have one, will have been given based on affordability and they'll have taken your existing liabilities into account.
To formalize that you are only a trustee of your parents house, you need a declaration of trust. Your conveyancing solicitor almost certainly can prepare one - although it might be that they will want your parents to take independent advice. The only thing you would need to make clear is that you are formalizing the existing position and there is no change of beneficial ownership - I don't know if this needs specific wording in the DoT or not. What you can't do is backdate the DoT - but that doesn't matter. When the parties trust each other, the only real benefit of a DoT is that it lets you prove the situation to others - for example, were you to be made bankrupt in the future you could prove that you never had an interest in your parents house - otherwise there could be a suspicion that you were attempting to hide assets.
You can google example DoT yourself. Whether a DIY one achieves what you want is your own risk. By using a solicitor you have someone to sue if the wording isn't correct and doesn't achieve what you wanted.