You could show us your ADSL stats to check your upload speed isn't 448k, in which case Plusnet would need to uncap your upstream speed if you're on a WBC / 21CN enabled exchange. Then the uploading wouldn't take so long, although it wouldn't fix the problem either.
Apart from that, assuming you switched to the Plusnet 2704N router, then it's a known issue with the current Plusnet router. Well, known to me, although I've not seen any acknowledgement from Plusnet that they've added it to their list of things to get fixed in the firmware for this router. If your previous router isn't locked to your previous provider, you could use that instead.