I am thinking of quiting my PhD. Do I have to return the funding in full or in part? I am 5 months into the course in the first year and it is not for me. I can not remember I signed any documents or contract Or any discussions about this sort of circumstances.

Check what your terms and conditions say... I received a whole booklet when I got my funding offer - it lays things out. Far as I can tell I do not need to repay if I leave but obviously payment will stop when I leave.

My understanding is most UK funded students don't have to repay if they leave.