Curry smell, damp patch in passenger footwell. Heater matrix is leaking. Two ways of dealing with this. First, tip a bottle of K-Seal into radiator & hope leak goes away, usually does. Second, rip out dash & replace heater matrix.
On Xantias & ZXs, Citroen allowed 12 hours. Fastest I've ever fitted one was 4 hours on a ZX, usually six on a Xantia. Did here of a meck-a-nic doing it in 2-3 hours but he had very skinny fingers & modified (bodged) the heater box.
Internet reviews on this CT1 Miracle stuff are quite varied. I'm always wary of something that has 'miracle' in its branding. I'll have a word with my local plumbers merchants, they'll know if its sh!t or not. Pricing seems to be dearer than K-Seal for something that does the same job.
Alternatively, pour some sodium borate & an uncooked egg white into the system. That'll stop the leaks!
H