Wow loads of responses thanks guys!
I'll see if I can remember all the questions to reply. The PlusNet router is the only network device, so they are all on the same segment. The PC and Pi are wired connections whereas the laptop is wireless.
As someone else confirmed my thoughts this is my local network so port forwarding is irrelevant. The fact I can connect to the Pi also confirms this.
I can ping the pc from the laptop but when I tried the reverse last night it did time out. I'm at work now so will check whether either of the machines has classed the network as public as that does seem like a good candidate for the issue!
Thanks for all the help!
