No pre-titles that I know of for French or Spanish fleets.
It would be tough to come up with a consistent "His Majesties Ship" for those two fleets in particular, as during this time period those two countries were going through some very serious political turmoil.
In the span of 1792-1815 (just twenty-three years) the french government was controlled by a monarchy of the Bourbons (King Louis XVI), the National Convention (under Robespierre after the bloody revolution), the Directory (during the Thermidorean Reaction), the Consolate (under Bonaparte), Napoleon Bonaparte himself as Emperor, back to the Bourbons (King Louis XVIII), back to Napoleon (during the Hundred Days after he escaped his first imprisonment on Elba), abdicated to Napoleon's son (Napoleon II) for a few weeks (after Napoleon surrendered and was banished to St. Helena, during which time Napoleon II was a four year old boy and not even in the country, being the daughter of an Austrian Duchess who fled back to Austria when Napoleon was exiled the first time), and finally back again
to Louis XVIII when the Allies finally took Paris and restored the Bourbons to the throne.
Likewise during that same period the Spanish monarchy changed hands from another section of the House of Bourbon, starting with Charles IV in 1807, passing to his estranged son Ferdinand VII for a couple of months before Napoleon placed his brother on the throne (Joseph I) for a few years (controlling very little, and barely managing to hold onto his title, let alone manage the Spanish Navy), and back to Ferdinand VII (as a political appeasement to the anti-French Allies by Napoleon) in 1813.
Not only was there no consistent "His Majesty" to credit the navies with, but the entire concept of having a king was in the air as the peasants, middle-class, upper-class, militias, and military were all revolting against the government at one point or another. The ships were literally controlled by whatever faction happened to be in power that week, or whoever the Admiral/Captain in charge of the ship believed
to be coming to power in the near future. The political intrigue at this point in history is quite a story, and honestly it's amazing that anyone
was organized enough to keep track of what ships there were in the fleet, let alone direct them where to go and what to do.
Long answer to a simple question... sorry...
Neptune" would sound a bit more grand???