Hi iSay, in lieu of anyone posting any other alternatives, I reckon I've found a really good, and not too expensive solution...
The
Sharkoon X-Tatic Sound Control Unit (SCU)
You simply plug hte SCU via TOSLINK into your PS3, and plug your 3 3.5mm headphone jacks from your Medusa Speedlink headphones into the matching audio ports on the SCU. Job done.
£57 from Scan.co.uk
Or if you're feeling flush, you can buy the SCU with matching 5.1 Surround sound headset for
£108.10, again from scan. The advantage of buying their headset is they've got their mic working with the PS3, so no more annoying bluetooth.
I can't afford the headset as well, so will just be buying the SCU, perhaps for Xmas.
As you're new to the PS3, I'll advise you that I don't think it's straightforward (maybe not even possible?? Someone correct me if I'm wrong) to get the Medusa Speedlink's 3.5mm mic working on the PS3...
So what I do (as I currently already use stereo headphones) is use a bluetooth device (Jabra BT8040) sat on the arm of the chair beside me, but in Audio Settings on the PS3, set my Bluetooth as the input audio device, but change the output to the "System Default Device", so people talking comes out the headphones, not the bluetooth. Think that makes sense. This way I can still talk to my mates whilst wearing headphones.
Hope that's of some help. Let me know on here if you get it and what it's like... Christmas is going to feel like ages away!