Repairing rust underneath scuttle panel.

[hippidy]

After finding an inch of water in the footwells I've found a couple of holes in the corners underneath the scuttle panel.


It's rough position is here:


Has anyone got any ideas on how to go about fixing it, it's the same on the passenger side but access is even more limited, I'm thinking I may have to cut a hole above it to get access but that would be a last resort.

Thanks for reading.