Good grief, you know our language police would be hacking away at any label that read "glaceed cherries". You are absolutely right, it is already a 'participe passé et adjectif'.

We never, ever, ever (am I being adamant enough, do you think ) add a D to our verbs to change the tense to the past. Since, in this case, it is used as an adjective I am sure you are right that it is an attempt to verbify the word (and it's not pretty). Two raspberries for the people at englishconsulting.com