Right I've done a lot of Googling on this too - most of the stuff I found was on American sites, and soaking in kerosene is very popular (I believe kerosene is the same as parafin?)
I was still a bit worried about it getting past the rings and diluting the grease inside the rollers, so I went for the spray-on chain cleaner. The one I got was Motorex - works very well. Spray it on, leave it to work for a bit, then wipe off with a cloth.
Then I went along the chain, link by link, and found a couple that were a bit stiff. A few more sprays and some wiggling on the stiff links got 'em sorted - but there was one link that was siezed solid! And I
mean solid! I ended up having to hold the chain in a vice and use a hammer to get the link moving again (along with loads of cleaner spray and chain lube). This has likely happened while the bike has been laid up, as it broke down while covered in salt and road grime
Other than that, the chain seems to be in good condition, it rarely needs adjusting and none of the links are too slack. Looking at service records, it looks like the chain (Tsubaki X-Ring) was fitted at approximately 20k, it's now on 33k - so it's done 13k. Front sprocket was changed 1k ago and rear one is fine.
This has taught me that I need to remove the chain and service it more often and not just keep spraying with lube.
I'll keep a close eye on it from now on
