My letter says that I am HPV positive, with Low Grade cell changes. What does that mean?

Your test has shown some minor changes (low grade) in your cells which require further investigation in a colposcopy clinic.
Finding out you have cell changes can be worrying. It is important to note that cell changes are not cervical cancer. Having cell changes also does not mean you will develop cervical cancer.  The majority of cell changes will get better by themselves or with treatment.