The interview process was extremely quick, i went from applying to job offer within a month. I initially had a Skype interview with Futureboard and while this was nerve wracking, the interviewer was extremely nice although seem'd to be quite bored (I imagine that she had to do a lot of them!) it lasted for 50 minutes and contained questions about why I specifically wanted to work for BT - i would suggest you did a lot of research (to which i stupidly didn't as I had a lot of university assessments at the time).
After the Skype interview, i heard next day that I had been selected for a particular company area and would require a phone interview with a member of staff from BT and this was undertaken 2 days after i had been notified. This was mostly a technical interview about what programming languages I knew and also some questions on those programming languages. These questions also included more generalised software development methodologies and their advantages and disadvantages so make sure you prepare for this!
I got invited to an Assessment Center the same day to attend on the following Monday in Ipswich. This is where you go and perform 4 exercises. Interview, Case Study, Presentation and a Group Discussion. This day was extremely well organised and laid back, there were graduates there who had been through the process before and therefore know what you are like when you are attending the center - they really made you feel relaxed.
A week after the assessment center, I heard that i have been offered a job in software engineering.
Overall, the whole process was very smooth and i applaud Futureboard, who work on behalf of BT for graduate recruitment, they did a brilliant job at keeping me informed throughout the whole process and giving me helpful insight into what I need to prepare for each stage of the process.