So....throttling...

[ptrduffy]

For the traceroute, the key thing will be the difference between the result with and without VPN.  If you could post the results of both that would be helpful.

[CJP]

Top, no VPN, bottom with VPN.

[ptrduffy]

There's nothing glaringly different between the two, other than the VPN route showing fewer hops (although it won't be showing the hops to the VPN server, I think) - the overall latency is roughly similar.

The only thing I can think is, as @wkirkman suggested previously, one of the routers on the non-VPN route is overloaded, or has a dodgy connection, and is dropping packets (packet loss requires re-transmissions, which reduces the overall throughput of the connection).

Unfortunately, there's not a lot you will be able to do about this.  It's quite possible that the problematic router belongs to a non-BT network operator, so complaining to BT is unlikely to have any effect.  The only real hope is that the operator in question notices the problem and fixes it.

In the meantime I think your best option is to keep using the VPN.

[CJP]

Hi.

Thanks for replying.

Just as a reminder, I experience no issues when I use my neighbour's BT wifi. A few doors down from me...

[CJP]

Potentially stupid question this...

...but could there be an issue derived from my own visible IP address?

[Les-Gibson]

It certainly seems like a strange one.

Sorry if this has already been asked but have you tried leaving both your hub and ONT powered down for a few minutes

[CJP]

Hi

Thanks for your idea.

Just tried it.

Powered down for 30 minutes.

Now up....and exactly the same thing. 

[countrypaul]

Do you still have the same IP address on the router as when you first discovered this problem? Just wondering if the IP address could be on a "black list" type of thing for excessive usage and being throttled by one of the intermediate routers. 

Not sure if you can force a change of IP address, but leaving your router off overnight might work to get a different one.

[CJP]

Just an update on this...

Don't think it is a blacklisted IP now as I've had a few since I last posted. I have been checking them.

Nothing has changed by the way, however, another peculiar event...

BBC iPlayer, ITVX, Amazon Prime streaming all work very well.

Channel 4's version of this is very very bad and pauses for buffering every 5 or 10 seconds. Guess what cures this? Switching on the VPN. So there's a clue.

That means, I guess, that it is indeed NOT a throttling issue.....but there is something really weird going on. All devices in this house have this problem, problem goes away when VPN used, yet it doesn't affect a neighbour. And remember, have had two different routers now.

[countrypaul]

Does a tracert on using your router give the exact same results as on your neighbours? Are the  intermediate routers that you can see the ip addresses of the same for both?