Just keep in mind that historically plusnet is the dirtiest player on ISP market and has a long and ugly history of overselling, limiting unlimited packages, shaping traffic, publicly shaming their own premium users into moving to other ISPs and ratting punters out to anyone who will ask. There are plenty of examples on ADSL forums of just how quickly plusnet management go back on their contracts and how ugly the fight gets once they start overselling their network capacity again and again.
Plusnet was one of the first, if not the first in UK to put asterisk next to "unlimited".
They were the first ISP in the country to introduce what was commonly known as "warez tax". Access to, let's call it, more shady parts of internet to anyone who was willing to pay a fee. Basically after several years of selling unlimited packages, at some point they just regrouped, blocked some ports, mostly P2P and incoming port 21, on all accounts and offer "unrestricted" package for extra fiver. This would unblock access to the notorious sharing ports and additionally allow access to plus.net's own binary usenet server.
Around 2005 they started overselling their infrastructure to n-th degree, and became one of the first British ISPs to invest in elacoya traffic shaping equipment to throttle users instead of expanding their connectivity. Almost overnight they went from selling unlimited packages with specifically enabled "alternative content" access to 50Gb cap,
stopped syncing their binary server with Giganews and started sending warning emails to users.
They were the first ISP in UK to introduce multilevel peak and offpeak allowances and remove heavy downloaders (if downloads over 50Gb a month could be called heavy). The brown, silver and gold traffic shaping "queues" as they called them, with separate SUP, FUP and throttle setting on each.
What I'm saying is - regardless what PlusNet advertises now, just be aware that for the past decade there is no such thing as anything "unlimited" on their network. Not for long enough to set precedence anyway.