Finally got round to installing the old 2-way splitter and the signal is fine now so its definitely the splitter. Appreciate all the help, thanks a lot.

Now regarding a proper 3-way splitter I'm guessing it safer to go with a powered one? Any suggestions? I'm struggling to find a 3-4 way powered splitter, most look like giant 8 and 10 way splitters which I have no room for. Do they even make smaller powered splitters?