This was a game I played in school aged 5 or 6 (in year one or two), which would be in 1991. I believe it was on a BBC Acorn, though it might have been some other computer; it seemed old fashioned to me at the time, anyway, so probably something from the 80s.
The game was, I think, very similar to Granny's Garden; blocky text interspersed with colourful images, educational/puzzley gameplay and a second person style of prose. (At least, I think there were pictures; I might be conflating it with Granny's Garden and it was actually just text). Since this was in primary school it was most likely an educational title (or edutainment), or something that was distributed to schools.
The only part of the game I can actually remember, though, is that at one point a troll (possibly ogre?) turns you into a frog (possibly toad?) and that, rather than being a bad ending, this makes you small enough to fit through a tunnel (or something) that you couldn't previously get through, so is required to advance to a new area.
I've tried checking out 4mation's other games besides Granny's Garden (Flower of Crystal, etc) but they still enforce copyright rigorously; from what I've seen on YouTube videos, though, it doesn't seem to be one of them.
Edit: I've been looking through some old BBC games, and screenshots by the company "Sherston Software" (for example, this game) seem fairly similar to my recollections, so it's possibly part of their catalogue. Unfortunately they seem rather poorly documented online, so I can't tell for sure - but the style of game matches up.