Hi Penny. We had a very difficult time house training Evie but as it was her problem did turn out to be medical. Does she wee more than you would consider normal? Does she eat OK?
I would just pop a sample to the vets and they will soon tell you if she has a UTI or cystitis or something. My tip for getting a non sterile sample is waiting till she does it on the floor then use a syringe to transfer it from the floor to the pot - much easier than following her around with a saucer. It could just be that it hasn't clicked with her yet but the fact that she is weeing without knowing (i.e. when sitting) suggests some urinary irritation. Good luck - let us know how you get on.