Not sure on the conditions in which it was stored - largely unused for a few years as far as I can gather. It was also very grimy when I picked it up so it did receive a very thorough wash. I worry that some water soaked into CLP during the wash but I think there is enough evidence that there has been significant damp issues accumulating over time as the radio damage suggests.

I'll check if the drains are plugged, slightly worried that this could invite water ingress rather than relieve it but have read a post about warping them slightly to prevent this so might try that. I'll have a look at the amp as well and see what meets the eye. Thanks again.