Significant Ping Problems!

Hello,
I would like to ask from anyone's experiences or suggestions about an issue I am currently having. (specs at end of post)

BTHomehub3 - download- 8Mb/s max, usually 52m/s ping
TP-Link AV500 Powerline adapter

Here's the deal: I have been having big problems with significant ping spikes if anyone else is on YouTube, or just connected to the internet. I have 2 wireless devices connected to my router, mainly my sister's iPod Touch 4G and my mother's Tesco Hudl 2. If either are on the internet when I am gaming in my laptop, I often have big ping spikes of up to 300m/s. Usually, if it is just me on the network, it will settle at 50m/s. My solution was to go for a wired connection, but my laptop is at the other end of the house to my router. So I bought a TP-LINK AV500 Nano Powerline Adapter Starter Kit for £24.99. I knew that wired was essential for any gaming machine, but I didn't think I needed it before. It didn't do much at all. Next, I took my laptop and set it up on a table next to my router, and plugged it directly in with a CAT5e cable. Still, seen as my sister was on her iPod, the download capped out at 6.5mB/s and I got 52m/s ping average (speedtest.net). Now I am thinking, I on my powerline setup, I used the cable that came with it, which was CAT5. I am now using CAT5e and there is no difference, but I can't see why there would be anyway because the only differences between 5 and 5e is that 5e is capable of transferring higher speeds, those speeds I weren't hitting.

If I use a CAT6 cable for each end of my powerline adapters, since CAT6 has 1.5x more bandwidth compared to my current CAT5e cables, will I have more of that bandwidth being stolen by my mother and sister?

This is primarily a ping issue, but if there is any download speed increase too, I'll take it. I realised about half an hour ago now, that ADSL max caps out at 8mB/s (bit of a coincidence, isn't it?), so if I upgraded to an ADSL 2 package, will my speeds increase, or solve my ping problem? I am up for buying a more expensive router if that is what it takes, I may very well do it.
I do not know which ADSL I am on, but this ADSL max cap is a breakthrough for me, and I have a feeling that that is what I have.

All replies appreciated,
Callum