The modifications range from small and simple to a bit more complex. A summary or what the modifications and additions are and what they add is below with links to more details.

Extending the gas cupboard to carry an additional 6kg cylinder eases gas anxiety and reduces gas waste to zero. More information here.

Changing the heating control to the digital version is cheap and easy to do and gives a much more controllable experience.
More information here.

New nozzle for kitchen tap to reduce water usage. This is just ace! Seconds to fit, gives better coverage for washing up and uses 50% less water.  This one comes with all the adapters you need and looks great.

Adding a 150w solar panel to charge the leisure battery. If you plan to wild camp more than a few nights running, and use a fair bit of power for the TV, charging and so on then this is worth doing. There’s also a natural feel good feeling about getting free energy! I did document fitting it but there are already plenty of good videos  out there.  If you want to know any Flash 04 specifics, drop me a line.

Finding the right wood effect vinyl to cover screw heads and blemishes and make any additions blend it. This is the stuff you need.

Automatic air freshener in bathroom.
The Glade Sense and Spray air freshner is the perfect way to keep the bathroom fresh. Every time you go in there it senses you and releases some arifreshner, perfect!
We attach it to the shelf above the loo using Velcro.

Bungs to plug the vents above the grill to prevent the breeze blowing in when it's cold. You don't want to permanently block the vents but you do need to do something about the breeze on cold nights and I'm very satisfied with this solution.

Other things I might add more detail on when I get time

Drop me a line if you want me to add more detail on a specific thing below.

Adding an extra dashboard light to make up for the woefully dim Ford Transit instrument binnacle is easy and means you can actually see the trip computer and dials.

Adding the missing bungs in the habitation door footwell that were causing the door mat to be perpetually wet..

Adding a removable table to create more kitchen workspace.

Adding an Amazon auto Alexa and new speakers transforms your journey.

Remove the horrid velour trim panel opposite the forward facing passenger seats to create some useful and attractive space.

Adding a Bose USB powered sound bar has transformed the TV and music experience.

More information is here.