I don't know who the Haddock-voice guy was in LAKE OF SHARKS, but, sorry Jock, it was not Paul Frees. (However, your point about stereotypes is well-taken, and Frees was a master at delivering them.)
Frees, though a ubiquitous presence in animated films, and at LEAST as versatile and busy as his contemporary, Mel Blanc, similarly had a distinctive timbre underlying most of his voices, as well as a few signature archetypes he defaulted to in certain cases, and it was those archetypes he used in voicing Tintin characters. I don't yet know ALL the Belvision stories that feature him, but I DO know that you can hear his distinctive take on the characters in SECRET OF THE UNICORN and RED RACKHAM'S TREASURE. He voiced Haddock as a blustery baritone, a bit overdone, but the richest and roundest-sounding Haddock of ANY animated version (including Nelvana). And he voiced the Thom(p)sons with what was then a fairly common American "take" on the British accent, very effete, nasal. slightly lisping, the sort who would punctuate their speech with "I say!" and "Eh, what?" a lot, veddy Terry-Thomas and Bruce Forsythe. He would also employ both the blustery old salt and effete Brit to comic effect as often as needed when he did voices (most notably Boris Badenov) in the ROCKY AND BULLWINKLE cartoons for Jay Ward ... among others. You can also hear him, in a voice close to his own, in the animated freature GAY PURR-EE, as Meowrice the Money Cat. He was also Donald Duck's eccentric uncle Ludwig von Drake, for Disney. Plus, in commercials, the Pillsbury Doughboy and Toucan Sam. He also provided Tony Curtis's "in drag" falsetto in SOME LIKE IT HOT. And it is Frees, in the Belvision cartoons that feature his Haddock, who most enthusiastically and memorably belts out the intro as "Hergeeeeeee's Adventuuuures of TINtin!!!" (For more on Frees, http://bearmanormedia.bizland.com)
The Belvision TINTIN series (and I've just now gotten reacquainted with several of the cartoons) seems to have had several sets of English-language actors (at least two, in whole or part), and if you include the voice of Haddock in LAKE OF SHARKS, at least three; the fellow voicing Haddock in THE CALCULUS CASE (sic) is neither the LAKE OF SHARKS guy nor Frees.
I can't assert this categorically, but my ear suggests to me that at least some of the Belvision stories were dubbed into English by British actors. Though I do still believe that LAKE OF SHARKS was dubbed by an inexperienced non-union -- and I think American -- cast. Aside from the voices being utterly unfamiliar to me [I was watching a LOT of cartoons back then, and knew well the "usual suspects" who populated Disney, Hanna-Barbera, Warner Brothers, Jay Ward & etc.], the performances are bad, and horribly directed, often weirdly or under-inflected, lacking the "musicality" of the seasoned voice-over artist who knows how to shade a performance that can't be seen, such that it fills out and inhabits a drawn "body.")
In fact, the difference between the Frees-voiced Belvisions and the others is quite stark. Aside from the assurance, professionalism and distinctiveness of the performances, there's also the giddy fun of realizing that EVERYTHING was voiced by only two guys. Frees handled the voices described above, plus various suporting characters. Meanwhile, Tintin, Calculus and Snowy (and supporting characters) were voiced by Larry Harmon.
Harmon (still alive) was himself a writer-producer of animation, his forte creating series from pre-existing franchises or properties. He was most famous at the time for having developed, licensed and voiced Bozo the Clown -- originally a series of LPs on Capitol records, created by record producer Alan Livingston and voiced by Vance "Pinto" Colvig -- which spun off into a number of children's shows featuring live actor Bozos, different ones in different regional markets, over 200 trained by Harmon himself (the Bozo show in Chicago is apparently still active, and the waiting list for tickets to be in the audience of kids is, like, a year). Harmon was a self-promoter as much as a character promoter and when enough years had gone by to obscure history, he took credit for having CREATED Bozo, and so thoroughly had his imprint infused the character and merchandising that the claim was readily believed by those who didn't know the original records (produced from the mid 40s through the mid-50s, whereupon Harmon acquired all rights to the character). Not long ago, however, the fraud was exposed, and Larry Harmon's plaque -- I'm not making this up -- was taken down at the Clown Hall of Fame.
Harmon also developed Laurel and Hardy for animation (the actual animation was done by the Hanna-Barbera studios) and did the voice of Stan Laurel. His last blast was co-directing (at least in name) and producing a live action LAUREL AND HARDY movie in 1999, called FOR LOVE OR MUMMY, that starred Bronson Pinchot as Laurel, Gaylord Sartain as Hardy and F. Murray Abraham (talk about a comedown from Salieri!) as the bad guy. The stars were swell, but the writing and plotting were forced and the film went right to video without a theatrical release. Yes, yes, I admit, I did rent it ...