Hi there Tracey and welcome to the forum
If you have proof of high travel costs you may be able to agree a higher amount. At the end of the day you can only start an IVA if you can realistically afford to keep up the monthly payments therefore allowing for all your expenses is in the interest of you and your creditors as long as you can offer a realistic amount to make your IVA viable.
You are not going to be asked to change jobs. Have a look at the BeatMyDebt.com IVA living expenses guide linked below. This will give you a better idea of what living expenses can be included. You may find that you spend less somewhere else which will allow you to put more to your fuel costs. However, as I said you should include all your actual costs when working out what you can offer in your IVA proposal.
I wonder who gave you this information originally?
https://www.beatmydebt.com/individual-v ... ses-guide/
Melissa McDonald writes articles and blogs about debt solutions and how they can be implemented. She aims to reassure people having debt problems that they can be debt free!