I was about to suggest that you download the Better Returns Programme parasite control guide from
here because it shows you all the meds, which class they are in, what parasites they affect and what stages (egg, larvae, adult, etc) - absolutely brilliant resource.
However, the doc at the end of the link no longer contains those tables - in fact, it's now mostly about external parasites - and I have been unable to find the tables elsewhere. I have emailed the BRP team to ask for their help, but I suspect they've had to withdraw the info as so many farms now have worms and flukes resistant to some of the meds listed.

However,
this document is useful in terms of approach to worm management.
I have a copy of the original document, with the tables, but it's way too large to upload as an attachment to a post or PM...
Remy, can you post exactly what nematodes and the other thing you didn't understand from the Post Mortem report and I'll look them up for you?