After scouring the internet last night for any potential fix, I find myself here, fairly unhopeful.
Long story short: the 3.5 patch is being an absolute butt to download and I mean that in the worst way. While the download starts good at 2MB/s in the time it takes for the launcher to display the length of time left on the download, we've fallen to 1.3MB/s - and that will then drop to the most abysmal 0.10MB/s I've ever seen. So we start at about a 15 minute wait time, down to about a 220 minute wait time.

The worst I've seen it drop to is 0.05MB/s and at that point I have a wait on my hands that I can't really afford. (And no, leaving the PC on all night doesn't appear to work, because when I woke this morning the download had failed anyway and needed to be restarted from scratch.)

Possible cause:
I figured perhaps it was an ISP throttling issue, but I then also figured this would make absolutely no sense. I mean, this is a brand new computer, so I had to redownload the entire game only two months ago. Which, I might add, took maybe two hours at max for the entire game to be up to date.

Solution tried: Everybody's favourite solution, VPN.
Which ironically meant that I had to get a proxy for my web browser, because Virgin just hates anything that's related to a proxy or a VPN, in order to access Cyberghost, in order to even try this solution in the first place. For the record, downloading a VPN through a free proxy service is about as much butt as trying to install this patch so far has been. I also had to change my DNS in order to run Cyberghost once it was downloaded and basically I've never had to do this before in my life for any other program.

Result: There was no result. Unless recommencing the version update instead of having to start from scratch counts as a result, but the download speed was still a fantastic 0.11MB/s at highest.

Possible cause: Maybe, I said to myself, my antivirus is causing a problem. Maybe the obvious problem was the one I didn't think about.

Solution tried: Whitelist the application.

Result: No, no that's my download speed dropped to 0.05MB/s for a little so that isn't much of a fix.

I'm all out of ideas by this point, so in an act of desperation I switch to the second internet connection in this house, hosted by a different ISP. Having made sure the game can pass through all my firewalls (honestly if it was an AV or firewall issue I'd expect to see the launcher not even load up without something telling me it's trying to block the application) and having used a VPN to no success, this was a long shot in the dark, but it was at least another option.

No change. We're still looking at over five hours of time needed to download the game, which sometimes improves to three hours if the download speed manages to stay steady at 0.10MB/s, which it never does.

I don't suppose anybody else is having this issue? (Particularly if you're from the UK and with Virgin as your ISP?)
Honestly I'd be less surprised and annoyed by it if it had taken this length of time to download the entire game and patch contents up to the patch just prior to 3.5, but in the amount of time it's taken me to try and download this patch alone, I could have downloaded that amount of content about seven times over with no problems.

Help a poor soul who just wants to run around murderating things?

(Sidenote: there have been several times this morning trying to load content on the Lodestone or the forums where it's taken a metric year to load the pages. What are the chances that it's a traffic issue on Squex's side causing this?)