Unstable pings, slow streaming. and downloads.

[#1]

For over a week now I have had very unstable pings, usually when I log into World of Warcraft I have a nice 50-70ms, But since recently that number goes up by like 10ms every minute and it doesn't stop till the high 200s.  When I try and download off rapidshare premium, I peak 60kbs, when I try and stream videos on youtube they tend take a while to stream. Now when I first subbed to Plusnet premium a few months ago, I had nothing but great service, great pings and download speeds.
Since recently, I have to admit, its been going down the toilet. My ping cant decide what the hell it wants to be at. I tried the router I used with AOL, the netgear, which btw I saw some improvement (strong 5 bars, constant 54.0MBps speed). Done virus and spyware scans nothing found.  I use gamebooster to shut down all unnesscesary processes for games, doesn't make a difference.
I thought usage allowance's are put in place to prevent strain and issues for the bandwidth. Its actually dire after coming back from a 8 hour shift, and I want to do some Arena to find that my ping is unstable, and I will suffer from disconnects. As of now, in WoW, my ping is 255ms., oh wait, its went up to 268ms, will it stop ?
I want to be sure that the Plusnet staff are aware of the issue, If it isnt a ISP issue, what things can i do to improve the situation?

[#2]

it's an isp issue , my ping was amazing (well for where i am) 26ms when i first got interleaving turned off , and my connection was even better when i added max premium (higher upload , around £7 on the bill) , but the last month has been terrible everyday i have to gateway hop in the hope of a ping less than 50 , half the time i give up.   Plusnet staff have been very helpfull tho, i just hope this problem doesnt continue

[#3]

On the unstable ping part; that is just PlusNet.
I will make a ticket after I shift some of the workload I have but basically from my understanding the network is hugely congested in peak times and as such you are routed through some sort of US servers, presumably to save money.
The exact same reason I cancelled with UKOnline has now spread to PlusNet unfortunately - its not exactly their fault Internet traffic has gone up so much in the past few years very few ISPs can maintain solid ping times and performance on peak for affordable prices.
Just ashame unless they fix it im off; considering consistant low pings are very important for me.

[#4]

Threads everywhere on matter mate. Apperently a fix for WoW coming tuesday, what they told me after complaining so hopefully that sorts the wow issues, wel see. But ive had this prob for months now, with the odd week being good.

[#5]

Everything seems to be running smooth today, but I wont hold my breath yet.