I like costuming detail a lot, especially when it adds to a character's story. So the medals for Jonathan and Norrell were interesting to me.
The two that only Jonathan have are:
1) Gold Cross or Peninsular Cross - what the Army Gold Medal evolves into once an officer has four or more Army Gold Medals. Each arm of the cross is inscribed with the four battles that the recipient distinguished themselves in, additional awards would be represented with additional clasps on the ribbon. Impossible to make out what's written on arms here, unfortunately.
2) Army Gold Medal (small) - awarded for distinctive action or command for high-ranking officers only (majors to colonels). This should technically just be a clasp on Jonathan's Peninsular Cross but production probably thought an additional medal would look nicer.
Jonathan wasn't an officer. He wasn't even a soldier. He technically doesn't qualify for these medals at all. Which means that Wellington was so pleased with his service in the Peninsular War that he allowed or authorized the creation of the position, "Magician-in-ordinary" (a title that sounds oxymoronic but in-ordinary apparently just means a permanent position instead of a temporary one), and gave it a commission equivalent to a high-ranking officer's. And then recommended "Merlin", who he found utterly useless in the beginning, for five distinctive actions.
(Notably, and somewhat unfortunately, Wellington IRL didn't like the idea of campaign participation medals since soldiers were being paid to do their jobs. So it was really only officers who were awarded medals for anything. The common soldiers got zip for their service.)
Anyway, well done, Jonathan. He went from being absolutely lost upon arrival to the Peninsula, idiotically proposing a rain of frogs to inconvenience the French, sulking about not getting any respect, and then slowly realising that his expectations of playing the heroic revered magician are stupid.
One of my favorite things in the story is the fact that the very first thing he does that actually helps anyone in the war has nothing to do with magic and only required him to be open-minded and respectful of others regardless of class: helping the illiterate soldiers read their letters from home. It's the first true split he has with Norrell's elitist ideology. His growth as a person and magician is only boosted later on when Norrell's books are destroyed and he has nothing to depend on (RIP Jeremy) but his own creativity and judgment.
Not a flawless process (the reanimated soldiers were a hard traumatic lesson), but the episode this all takes place in is called "The Education of a Magician" for a reason. For better or worse (mostly worse and deliberately done), Norrell was holding him back from the growth he was capable of.
It's also a nice little background arc for Wellington (Lord? Duke? Arthur Wellesley?) to become so dependent and supportive of Jonathan over the course of the war. Though not-so-great later on when Napoleon comes back and Major Grant says that Jonathan, who was literally about to leave London permanently with Arabella so they can just be a normal happy couple, isn't allowed to say no to Wellington's "request" to renew his commission. "Merlin" again served well in the Hundred Days War though the show only showed us a short flashback to the Battle of Waterloo. But it cemented Jonathan as "Wellington's man" which was enough for Grant to get him out of jail later (if Jonathan hadn't escaped first lol). And in the book, Wellington remained steadfast in his support of Jonathan even when Parliament was questioning him about Jonathan's very public and very terrifying descent into madness.
I can't identify the last medal, the one that both Jonathan and Norrell have. The show is over a decade old though so someone in the fandom must know. Please tell me if you do.
It's not a military medal (signified by the different ribbon) since Norrell was certainly never granted a commission and the army didn't rate his spells as useful, in any case. Norrell contributed in his own way, but away from the front lines and preferring to do only "respectable" magic (which limited those contributions), the only people who would have really appreciated his efforts were the lords in London. So the medal was likely created specifically for magicians since civilian medals didn't really exist in this time. Or as a response to pacify Norrell in anticipation of him being displeased about only Jonathan having medals (since the reason Jonathan isn't awarded a lordship is because Norrell would have to be given one too as his teacher and no one in parliament can stand to call Norrell "my lord").