Had online psychometric tests, an over the phone interview followed by a two day assessment centre up in Cheltenham. The tests were the same as you do for any engineering job (verbal reasoning, numerical reasoning and logical reasoning) and the phone interview was around 35 minutes of them asking you competency based questions such as "Why do you want to work for EDF?"... "Explain a time when you had to work as part of a team". And so on.
The assessment centre was a bit laborious and was over two days. On the first day 3 group activities and basically the same style of psychometric tests as before only this time in a controlled environment. The group tasks were to build a model of a windmill using only pictures in a given time, a discussion about which projects to choose for nuclear new build and a logic exercise trying to work out who worked where using prompt cards. Bear in mind that the tasks are a sideshow, the group I was in finished none of the tasks and I was still given the job so make sure you get your points across in the time.
Day two is technical interview day and those who were unsuccessful with the first day leave the process first thing after breakfast. Technical interview was asking about final year projects at uni and then draw a nuclear power station. Make sure you revise the components of such a system and be honest if you don't know the answer. They will ask you questions of increasing difficulty until you say "I don't know".
I was informed almost a month later via email that I had been successful, so if you haven't heard back don't be disheartened.
Medical and security clearance happened over the easter period at one of their power stations.