Water is leaking from the blower into the footwells of the Saxo and I've been advised to firstly try some radiator leak additive,does this actually work and is it a permanent repair if it does, or should I be guarded to a replacement matrix being inevitable eventually.

Should the matrix need to be replaced does it involve removing the whole dashboard for access, and can anyone advise on that process and how long would it take.

Thanks for reading