Would just like to add, If you have symptoms such as post-coital bleeding, that a cervical smear test is not the only test that a GP should do. Indeed as someone else mentioned earlier, it is a screening test not a diagnostic test. The GP should refer you to Gynaecology clinic for other appropriate investigations. i've known of patients who did have cancer but the GP was waiting for the test result - we do them pretty quickly and directly refer to colposcopy ourselves but the patients could have been seen even quicker if they'd been referred by the practice. Anyone one with those sort of symptoms can be referred as a 2 week wait.
to explain a bit further about what your cervical cells look like, I've copied from another post of mine:
The cervical epithelium matures in line with your hormones, a bit like the endometrium. At midcycle it's most mature and so the cells are easier to interpret.
Many women will have low grade changes/abnormalities which go away without needing treatment, that's why some people have follow up samples not colposcopy.
This is because the body can clear HPV infections given time. Some people don't clear the infection so quickly and the virus then can act to make the cells more abnormal. But this won't be the case for everyone. There's not a test available yet to be able to tell the difference between which would carry on to cancer and which wouldn't. That's why colposcopy and treatment is needed for these precancerous changes.
Part of puberty involves changes in the cervix. The increase in oestrogen causes the cervix to get bigger in volume and the cells inside the neck of the uterus (the endocervix) to be everted. Imagine pouting your lips outwards - the skin inside is really soft and not 'built' for being exposed to the outside. The same thing ahppens with the cervix. To adapt to its new acidic environment of the vagina, a process called Metaplasia takes place, and more durable thicker squamous skin grows in its place.
During this process the cells are really active and are difficult to interpret. Abnormal cells are also really active. In the lab we're looking the nuclei of the cells in great detail.
This common ground makes it more likely the under 25s could end up being overtreated for minor abnormalities that could go away on their own if give time.
The treatment usually a LLETZ or LEEP can have some fertility implications,so again, this could have major problems in the future for a younger woman.
As MJM and Sawyer said, it is a screening programme, for a whole population, and it needs to be used in the most cost-effective way.
Anyone who was already in the system when the changes to the age range were made, will usually have been kept on recall.