Around 5 million ZX Spectrums were sold between 1982 and 1992. If all were sold in the UK (they weren’t), that would put the penetration around 25% based on the number of households in 1990.
replyOne specific model of ZX Spectrum, which is one specific make and model of home computer.
replyDid you live in the UK in the 1980s?
Asking chatgpt, in UK in late 80s, it would be 20-25% across all computers, depending on definition of "computer". A 1/4 of households is still high. It may have been higher in your neck of the woods.
reply> Did you live in the UK in the 1980s?
replyYes.
> One specific model of ZX Spectrum
I do not believe this to be the case, that number appears to include the 128K and the Amstrad variants also.