Hello :-)

I applied for quite a number of PhDs in January and early February - all fully funded and in physical sciences - but have not heard anything back from any of these regarding an interview or declining my application. How long should I wait to hear back from these? Most state that it takes 4-6 weeks, but surely interviews must already be underway? I don't want to come across as impatient, but also don't want to seem as if I've forgotten and don't care about my applications.

Any advice or knowledge about this is much appreciated, thanks.

I think 4-6 weeks are usually for those who applied with their own proposals, for funded projects there is usually a deadline for submitting proposals. After that deadline the relevant academic staff will start evaluating each proposal. Perhaps check if there's any deadline. It really doesn't matter to send an enquiry asking the process of your application. Or you can simply call the admissions. Hope that helps.

Mine all took longer than the specified times... I kept chasing... no harm in appearing eager!