Sorry musta missed this earlier
I do believe that BB+ is not running as it should - bit out of touch with all thats been going on in the PN world of late Im afraid.
Because customers Pay per GB on PAYG their traffic gets priority and there is supposed to be very little shaping on any protocols. Http should get full wack.
BB+ http should also get full speed, but there have been a fair few complaints that its currently not doing if you use more than xGB.
PN are running short on capacity right now.. and Im hoping that things will get better when they install a new central due at the end of the month.
If you use less than 2GB per month then its certainly worth changing to PAYG - cause PAYG with 2GB included is the same price as BB+... and its free to swap over.