Have a look on eBay, lots of top quality CD players from the 90s. Or there’s an argument that some later DVD players are better, these can be picked up brand new for under £100 and will play cds and cdrw’s .

for example..

https://www.amazon.co.uk/dp/B007NXAD5O/ref=cm_sw_em_r_mt_dp_TNEDTXYFW2VPX8DA5GQN
 

If you don’t need anything fancy, you could use a small portable CD player with an AUX/Line output and connect to the Five using a 3.5 mm audio cable.

Do you have any recommendations on one to use? If we can just use a portable that has a 3.5mm audio cable, that is perfect! I will get the Five with the CD player and call it good :)

Would it literally be as easy as this?  https://www.amazon.com/Deluxe-Products-Portable-Walkman-Relaxing/dp/B083WNRH45/ref=sr_1_11?dchild=1&keywords=portable+CD+player+3.5mm+audio+output&qid=1631735677&sr=8-11

Connecting the CD player from the headphone port to the Five would work, but I’m not sure how the audio quality would be. Ideally you would want to find a CD player with a dedicated line out or AUX out port, but it seems they are a little difficult to find these days. I remember the old Sony Discman used to have a separate line out port. You could possibly find a used one on eBay for pretty cheap.
 

Another option is a compact DVD/CD player like these:

https://www.amazon.com/Player-Region-Output-Included-Supported/dp/B08319XH53/

https://www.amazon.com/Provided-Contains-Control-Supports-Playback/dp/B08DKZW2FH/
 

You would just need to connect it with an RCA to 3.5 mm audio cable like this:

https://www.amazon.com/AmazonBasics-3-5mm-2-Male-Adapter-Stereo/dp/B01D5H8JW0/

Agree with the challenges of using a headphone port. You end up messing with both the volume out on the CD player, and the sensitivity of the line in on the Sonos, and it’s never great. Can be done, but sooner or later someone will accidentally nudge the volume out on the CD player, either by mistake, or wanting to make the music “louder”.

Much better off with a line level output from the CD player to the Sonos. Safer, I’d expect, although I’ve never heard of anyone “blowing out” a line in before. 

So the better solution is to use a player with the RCA and use a RCA to 3.5mm cable (vs straight up 3.5mm from a CD aux output)?

It’s not necessarily a better solution, it’s just a different solution. Either solution will work just fine. But of course some players might sound better than others.

Looking at ebay there are some great CD changers available, cheap. Having even a 5 disc changer is a huge improvement as it will play them in turn and you aren’t running to flip discs. I prefer the tray types as they are faster to load and change CDs.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l2632&_nkw=home+cd+changer&_sacat=32852

Just single players are cheap too.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=cd+player+single&_sacat=32852&LH_TitleDesc=0&_odkw=component+cd+player+single&_osacat=32852

At best, the headphone out will work as well as the line out - the former goes through another cycle of amplification inside the player that can at times affect signal quality. But if a cheap one does not have anything other than the headphone out, it is worth a try over spending time and money getting a line out equipped one. I had to resort to this route with a TV that has just that output jack, and it works fine.

Going to give this one a try first: https://www.amazon.com/dp/B08TRWN63Z?psc=1&smid=A3MGJXQ37XI9ID&ref_=chk_typ_imgToDp 

Thanks everyone for the informationand recommendations!