Hi Trusted186. It may be possible, but you will need to be able to show to your trustee why it is necessary and that it is affordable.
Will the finance payments cause you any problems with sticking to your contributions as proposed to creditors in the first place?

No not at all, this is a bit of a winded story so bear with me, I originally had a car on finance at the start of my agreement but was allowed to continue with it due to needing it for work and being a secured debt, since my last annual review (2020), the car has since broken down, I managed to fix it (being a mechanic)to a place where i could ask my finance company for a voluntary surrender, they agreed but I had to pay the difference in value of the car vs what I owed, I was lucky enough that my partner had some money by that she paid off for me and bought me a run about that is now on it’s last legs but I still pay her back in installments, the worry is that because the money isn’t going to the finance company that they will now try and put that money towards my agreement which I couldn’t afford and then not have a car for work, so just looking to see what my options are, the instalment that I’m paying to my partner and the finance for the new car will come to under the payment I was paying on my original agreement

I don't think you should have too much to worry about, Trusted186.  The type of arrangement you have seems perfectly reasonable given the car is a necessity and as long as you are still able to pay at least what you were paying previously into the Trust Deed. 

You should be aware though that there is a possibility that you may be asked for a slightly higher monthly contribution if you can afford to do so once those revised costs are factored in.