May be using AWS for there own site shows they can manage a complex set of web applications in such an environment.
Maybe there site is a target for DDOS they didn't want there customers to be affected by an attack on there website.

Many company's resell services such as AWS, sometime customers just want to fire up an extra cloud server for testing. Why / how could a small company compete with AWS?
Sometimes customers want an AWS service but need a service wrapper around it too. Maybe they want a DB or App server hosted in a much more secure / stable / ... way than AWS can offer them but there front end web servers matter much less.

There are many and varied reasons for wanting to use a service such as AWS and for not wanting to deal with AWS directly.

In reply to a post by Samadeus:

I can't believe you're actually serious, what does it matter where they host their website? AWS have resillience that smaller ISP's can't begin to hope to replicate, you can have resillience across multiple continents if you so wish. If an ISP chooses to host offnet in a resillient way using a product they sell what concern is it?

I am very serious, Zen have a massive hosting/datacentre division (as well as web dev) and boast all this uptime and expertise and private cloud, and then go and host their own website on someone elses equipment. What sort of message does that give out to customers? Why on earth would an large business ever consider using Zen to host any of their servers etc when Zen don't even host their own website on their own servers/infrastructure?

This is what happens though when people at the top who are not technical (or even business oriented tbh) make silly decisions on cost cutting grounds.

Remember an ISP is a technical business selling technical services, as such it should be doing all this stuff in house, not doing it in house just gives out the wrong message.

In reply to a post by mixt:

But their roots are in broadband. I called them up over a decade ago to enquire about Linux hosting (dedicated servers) and they were not even offering those. I admit, I found that odd at the time, and personally, that was enough to demonstrate to me that they were not a serious hosting provider, certainly compared to other companies around at that time. So in my opinion, hosting has never been their strong point anyway; purely an after thought for a company founded by the demand for broadband in the UK.

Zen push their hosting offering very strongly actually and were very quick to shout about their amazing datacentre in Rochdale etc. I am sure it is very amazing too, so back to the original point you need to wonder why they aren't using it for their own web site.

On a somewhat irrelivant note, look at the TalkTalk hackings, let's say Zen get targeted, do you think they would be able to detect and shut down the hacking attempt on Amazon AWS or if it was hosted internally?

If you have built your own datacentre, claim it is amazing and want to sell it to people, the use it yourself... It's kind of obvious.

We are currently evaluating a hybrid approach to hosting our web sites using a combination of our own infrastructure and AWS. The thinking behind this approach is to give us a higher level of protection against DDoS attacks compared to using our own infrastructure alone. This was prompted by the recent DDoS attacks on our web site. We have not yet decided whether this hybrid approach with AWS will be permanent or whether we�ll remove it in favour of other DDoS mitigation techniques.

We take the security of our infrastructure very seriously. Our infrastructure is attacked on almost a daily basis and most of these attacks are mitigated successfully with minimal or no customer impact. When an attack impacts us � for example, the recent DDoS attack taking down our web site for several hours � then we commit to strengthening our defences so a repeat attack is less likely to cause impact. To strengthen our defences, we will pull on whatever resources and technologies we have available to us.

Zen has its own geographically resilient Cloud platform that is used to power mission-critical applications for a number of our customers. We are also an AWS Consulting Partner and deploy & manage AWS-based mission-critical applications for our customers. Zen Cloud and AWS complement each other. The choice of Zen Cloud, AWS, or a combination of both, for a specific customer depends on that customer�s applications & business needs. We have a team of consultants who assess the needs of our customers and recommend the most appropriate solutions.

Within Zen we have a large and extensive estate of our own infrastructure, but also use AWS in places where it makes sense to do so.