'94(N) Clio with corroded imobiliser circuit. :(?

OK- so my problem seems along these lines. I have a '94(N) Clio RT Auto with manual SR. After a night of heavy rain, water started pouring into my lap when cornering. I removed the sensor mounting and the sunroof handle and found the whole section full of water which i dutifully emptied and dried as best as poss. Drove it fine that day. That evening i went to start it again and it was dead, but all the electrics worked. Just no va va voom. That night more torrential downpours... BUT no more leaking sunroof, so i'm optimistically thinking maybe it wasn't done up properly the first time. However, i took out the sensor and the circuit board is corroded at the IR sensor end. One of the three IR sensors has come off, and another blue "chip" thing just behind and to the left of the IR sensors has come adrift by one of it's two points. This leads me to think that in order for that level of corrosion it has to be an ongoing problem. I have only had the car for two weeks. Sold as seen...sigh.

The Imobilisor light on the dash is doing nothing at all- just comes on when you turn the ignition and then goes out even though there is no starting noise. I tried depressing the central locking button while the ignition was on but no change at all. (This was before i took out the circuit, i tried it after as well and still nothing)

Is it worth getting the circuit microwelded or can i get a replacement? Thanks for any answers in advance... :)

Pip