An episode of Starstrider can be seen here: https://youtu.be/zgGT_gKuakM.
Funnily enough, I had no memory of it when Canadanne mentioned it earlier, but I do now dimly remember watching a few episodes of it. At the time, I associated McCoy only with Tiswas and Jigsaw, so it had to be before he became the 7th Doctor, although I didn't recall the series being as early as 1984; if pressed I'd have said about 1986 or 87. Roger Sloman is the host, and you might recognise him from plenty of TV in the 1980s and 90s, especially playing bureaucratic, by-the-book types, or yokelly farmer figures. Remember Three Fingered Pete from the sixth episode of The Black Adder? "Good shot! Looks like I'm going to have to... cheat." That was him.
The odd thing about Starstrider in this episode is that he looks like he's wearing Lord Fear's cloak, while, unfortunate sign of the times, blacking up as Ah Wok! Another sign of the times is the kids in the audience laughing much too loudly under clear instruction from the floor manager whenever something silly happens. Notice how the contestant on the bucking buffalo gets away with saying The Rocky Mountains are in South Africa, then changing it to South America, and she is still given the point, even though the Rockies are of course in NORTH America.
The only regular round I can remember is the one where the have to walk on the lit up slabs. Step on a pink slab you score ten points, step on a white one you lose ten.
The only other thing I very vaguely remember for some reason is a scene in one instalment where Wart (SlyMac's character) tries to find a purpose for a toffee apple, and Starstrider tries to explain that Wart has to "put it in himself," which seems decidedly naughty for a kids' show. They come from a planet where no one eats, where eating is a completely abstract concept, and so Wart spends the whole show experimenting with stuffing the stick up his nose, and in other places, before inadvertently eating the apple and finding he rather likes the sensation of taste.
In short, not a terribly good show. And no, getting actually to the point; I have no memory at all of ANY episode I saw in which someone fell into lava. But then I doubt that I saw all the episodes, it wasn't exactly the highlight of my viewing week.