Apologies if this is a little late in the day but there is no doubt that calculations for your net income from either Umbrella or Limited Company should all be standard.
How they are displayed is up to the company doing the calculations, and yes I guess each company will try to make it look good for them.
This
link has a spreadsheet and video explanation for Umbrella, Limited Company, PAYE with the agency, Sole Trader and Partnership.
You just need to enter contract rates and expenses.
For each structure there are detailed calculations showing the tax and
ni to be paid and your net income.
It may help, if its not too late !
Phil