Ok, so still don't have my garage back, so started playing with creating my own Hex Editor.
Before this, I would need to get the file from the car, use a free version of commercial software to open the file find the maps. Copy to Excel to do some fancy calculations and stuff to change the values. Use a free version of a Hex Editor to then find the right addresses and change the values in the Hex file. Then save that, checksum it, and load back into the car.
So I created an Excel Workbook that will do all but checksum (for now). Now I grab the file from the car. Load it directly in Excel where I can do all the work. Then the workbook will directly change the values in the Excel file and save it as a Binary file ready for Checksum and loading. The workbook does all the required conversions and has the normal configuration. Much easier to do it all in one place and have all the power of Excel directly available.
Here's a link if anyone is sick of fumbling with trial versions of commercial software while searching for Hex addresses, and can't afford to buy the full versions. Make sure you enable Macros otherwise nothing will really happen.
https://payhip.com/WG2004
Totally free, no restrictions. Been using it with my ECU and TCU with no faults or problems so far. Do your own checks before trusting it though. As always, donations are greatly appreciated.