smartdns issues invalid http response

I've been using a smart DNS service for 10 months and it's never really worked properly. I was originally on Vodafone ADSL, but upgraded to VDSL.

The issue I'm getting is as follows.

Websites fail to load images and style sheets, including but not exclusively BBC iPlayer and Netflix.

I did some investigation and discovered that some of the response to http get requests are taking exactly 40 second and the payload always contains only

For example one request was for a jpg image, but the response took 40 Second and the payload was so the browser would just display a failed image icon.

This problem is also affecting the on demand apps on my tablet and smart TV. BBC iPlayer app gets stuck loading or loads but thumbnails fail to load.

What I'd like to know, is if anyone else has experienced the same issue, or better still has been able to resolve it.

Cheers

Paul