I believe the primulot is a progesterone (P4) hormone tablet, by taking it for a few days and then stoppping, it effectively drops your P4 levels which brings on your period.

Serophene is also known as clomid. Generally it is taken for 5 days from CD2 or CD3. It turns off your pituitary gland for the 5 days when you stop taking it the gland turns on and says "boy I better get producing follicles" so it effectively promotes follicles and thus ovulation. The scan would be prescribed to monitor the follie growth and BTs would be prescribed to monitor oestrogen (E2) and lutinising hormone (LH) - the E2 is for endometrium lining thickening in the follicular phase of your cylce (also indicating growth of follies) and the LH is for detecting the LH surge indicating ovulation.