"There has been much discussion on the issues but, AIUI, the major issue is getting a sufficiently high signal level. So my interest perked up with the mention above of a Maplin pre-amp ... then waned again when I saw that it is no longer available."
A turntable must be properly amplified to get a recordable, line-level signal. The mentioned Maplin pre-amp is one example of a suitable solution, though not a very good one at that. You can find a similar device at most good hi-fi stores.
The mic input on an Iyonix (or other) PC does amplify the signal going in, but to a different level, so any turntable output directly recorded via the mic-in socket will sound distorted and generally not so pleasant.
I think it's about using RO for these sort of things, but you're certainly right in that it's probably easier and cheaper to use a stand alone CD recorder for it.
Ofcourse, you could use the computer to convert the music to mp3, for example. Or producing a re-mix using Tracker software if you're so inclined The best RO audio editing / processing software atm is SampleEd. It supports LADSPA plugins, which are a common format for Linux systems. There's a fair chance that you'll find a plug-in which attempts to eliminate surface noise or pops / crackles.