Ethernet issue

Because you are using multiple devices its like connecting 1 lightbulb to a battery it will shine bright, when you connect 2 light bulbs to the battery they both dim and when you connect a third they are barely producing any light your issue is your 30mbps internet is being split into all of those devices you wont get 30mbps in each device

Even if the ps3 is the only one using the internet at the time?

Well is the ps3 is the only one on the network thats a different story

Yes any ideas as to Why It's slow?

To be honest no my expertise is in computers not network management   il see what i can figure out.

All the cables are high quality so i just dont get why its slow. Is it the distance of the cable? Ive read that its good for 100m..  

What are you plugging this is into actually. There really is no such thing as a network splitter. It is likely a switch or maybe in worse case a hub.

The most liklely problem is that your ports negotiated half duplex on you ps3. You could also have it running at 10m but its strange that you get 14m then. I would take the PS3 and remove the switch and plug it directly into the cable going back to the router and see how fast it tests

OK thanks it is a switch. I'll give it a go