That's like saying "oh it normally only takes 30 minutes to get to my house in Cardiff, and yet I've already been driving for 5 hours from Scotland and I'm still not there, I'm stuck on the M42 at 5.30pm, that never happens on the M4 at 2am!"
Your download is made up of millions of tiny packets of data, all negotiating something fairly similar to the UK's road and street network, except it covers the whole world. There could be any kind of bottleneck or problem anywhere, you've really got no control over it, as above.
The bit between your laptop and your router is far quicker than the bit between your house and the internet, even with a poor wifi signal. If other downloads or webpages are working fine then you don't need to mess about with wires.
8Mbps = 1 MBps
Snot quite as simple as that. There's a lot of extra information being transmitted besides your actual download, and that depends on a whole host of factors. To download a 10MB file in an hour could take many more than 80Mbits actually being sent. There are loads of variables, so it's actually much fairer to quote megabits not megabytes. Plus stuff like video streaming and online gaming work completely differently to surfing and downloading files.
Or, to put it more simply, it could be their end that's buggered.