@Peter:
You quoted the MMC4000... I thought you got the wrong post or something... Sorry!
The passage above states that the styluses can replace thouse in certain cartridges - one of those mentioned in the SP15. As you know, the SP15 was the original cartridge for the Beogram 4000 and is, to all intents, a MMC4000. This bit of information was therefore wrong and I didn't want it to be quoted in future.
I wonder if they ever planned to allow the stylus to be replaced in this line of carts? I think it would have been possible in a way similar to the SP range!