8.1 has indeed rollout out in the UK in Q2 of this year, which as I indicated is when Cortana was expected but Cortana wasn't part of that update it's in the Lumia Denim upudated that is rumoured for Q1 2015 just as soon as MS give it to the operators to test. Only downside is no Jen Taylor doing the voice.
Well Cortana is availble on the newest models but not on older models, as for why it's so complicated over here, the problem is not over here but over on the other side of the pond, as MS hasn't released the relevant update for the operators to check to make sure there are no issues with any software the carrier has on.
This is what mine has to say
Hi all,
There have many many discussions and comments here on the community about the status of this update. We've also received tweets and Facebook messages - so we know as ever, this is a highly anticipated update that all of you are waiting anxiously to receive. And we can see why - Cortana herself is worthy of an update like this.
The Lumia 930 has already received the GDR1 update that includes Cortana... Where are the others? It's coming, but we're not expecting Microsoft to release these this year we're afraid, though you should start seeing them push out to Lumia devices in early 2015... Very early - January at present is what's looking likely.
We understand the wait may disappoint some but with so many Lumia devices out there, it's understandably going to take Microsoft some time to ensure these updates offer a smooth and reliable experience for all customers.
From what I've read there seems to be very few issues if you change you country setting to the US from the UK and download Cortana all indications that it seems to work on UK handsets so something else is at work. From a customer service point of view I would say MS performance leaves a lot to be desired, with slow rollouts of updates or them pushed back months it might make people think twice about getting another Lumia when their contract comes up. It's all very well attracting new customers but you don't want to lose your existing customers who might very well disuade others from buying a Lumia because of what they percieve as poor service.
Some UK users are disspointed that it's not Jen Taylor as the voice or Cortana but rather a UK voice. Which MS says is all about tailoring it to the local market, still no reason not to give users the option of selecting which voice.