I had my viva on February 12th - a nightmare, there were no questions about what I had done, only questions about what I hadn't done, mainly about not referencing more American literature to my research.

I was told there would be a meeting March 18th and I would get formal feedback.

It is currently April 9th - and I have heard nothing...has anyone else had a similar experience?

Can I ask are you a PhD student or Masters student?
If you are a PhD student, I would be immediately on the phone with your supervisor asking for an update. However, master's vivas results are usually part of the internal review process and can take this long.