All CVH's (and Zetecs for that matter) are favourites for losing a lot of voltage thru bad leads. This always shows up in starting when cold/damp .. The old favourite for a CVH that was iffy to start in the cold/damp, was to change the cap/leads, and check the R Arm for tracking/burning.

Also, the amplifier can just fail "out of the blue" If you stressed it in some way, plus it got cold/wet, this also could have failed (about tenner from factors)