Hi London elite,
I didn't mention the duty of care as I was quite shocked and upset at the time and just accepted what they said and let them rebook me for Wednesday. It was only after it was over that I had a chance to think a bit more and search the internet and check the forum here, that I found out about EC261 and duty of care etc.
Edit: I just didn't think to ask for a hotel or anything like that and nothing was offered, if anything the staff seemed a bit lost and confused about what to do too. Also the flight was full (I think because yesterday's and Mondays if I remember correctly are both cancelled).