Also, do I remember reading on here that the CDR500 doesnt really like CDRs??
Correct - never designed to be compatable 
And now for the deluge that will now post saying that their unit may play them 
I have noticed that Philips players in particular seem to be more prone to tired lasers after a lifetime of cdrs. Is that your experience?
I have a Carin unit here that spits out all disks, and when I acquired it it had CDR in it. Mrs TheBoys changer in the Rover (R770 HU, I think 036 changer) is Philips, and seems to be troublesome now

(though it is 10yrs old, so can't grumble)
The changers in my Omegas (CDC2) seem to fair much better, but don't like cheap media, so Verbatim only. My old 10 disc Kenwood from circa 1992 is still going strong, and has been used with CDRs since I got a writer mid nineties when they first came out (at 'sensible' prices (ie in the £100s)).
Is it a case that whoever supplies the lasers for the mechs used in early Kenwoods and the CDC2 are more suited than the Philips (who presumably use their own?) lasers for CDRs, and are able to focus on it better?
Or is my experience uncommon?