Q:

Windows Update downloads are very slow

I'm hoping somebody can suggest a solution as Microsoft help have been unable to provide any ideas.
I'm trying to download updates for Windows 10 from the inbuilt update utility and from the Windows update catalogue.
All downloads from Microsoft sites which go through Akamai are very slow, yet I can get download over HTTP from other sites at around 2mb/s.
From Microsoft sites, downloads average 200kb/s from MSDN, but for updates they frequently drop as low as 7kb/s.
I know people who have seen better download speeds using Google's DNS, but I'm keen not to change my DNS as my ISP provides support for DNS issues.
If anybody can shed some light on any possible alternative causes for the slow download, I would be grateful for any other avenues of investigation I might follow.
Many thanks.

A:

To clarify the confusion regarding this issue, the resolution was to refer the issue to the ISP who changed the routing  profile on the account.
I do not like to answer my own questions, but as the solution was derrived from suggestions in the comments and this thread has been commented on further, for the sake of completeness I have summarised the comments here as an answer.
Diagnostic steps suggested by Ramhound led me to the solution - 

You should verify the problem does not exist if you chnage your DNs
  temporarily

This yielded a slight improvement, but nothing major

I've tried on Google's DNS again, and am seeing a marginal increase in
  speed - roughly 40kbps rather than 7kbps, so it's an improvement but
  hardly usable. I'm starting to think that this is just a poor speed
  for the UK. If that is the case, my options are pretty limited.

After speaking to the ISP, it seems that the DDOS referred to by Ramhound was a contibuting factor. 

There is also a major DDOS attack that's recently happening/happened
  effecting numerous sites since Akami is in the center of that (one of
  th few services like it) you could be using a path to your destination
  that's being attacked

My assumption here is that the routing profile on the account with the ISP was part of the issue, and the DDOS was likely not helping matters.
If routing through to a different location resulted in an unaffected CDN server being selected, it would explain the improvement accounting for both issues.
It's conceivable that the problem was caused by either one of those problems, or a combination fo the two.
Regardless, the issue is now resolved. 

