The age of cervical screening is also 20 in Wales. I'm 23 and from South Wales originally but I live in Manchester (I was invited for a smear test at my local practice in Wales but never went for one because I was scared that it was going to hurt). I asked my nurse about it and she refused because the age is 25. Although she didn't take a swab, she did look at my cervix and she did notice an ectopy of the cervix (cervical ectropion). She said that it's likely that I have pre-cancerous abnormal cells which is harmless in the majority of women but because I had expressed my concerns and told her my symptoms (pain during and after sex, bleeding (spotting) after sex etc) she told me to speak to a GP about getting referred to see a gynaecologist and to tell the GP that she recommended it which I did so I'm now going to get it checked out in October. As for the smear test itself, I don't think the gynaecologist will be able to do one for me so I will be going private if I have to.
Mind you, every woman is different. I've had problems since starting my periods, heavy irregular periods, hormones were f*cked up among other things. Also, it depends how early you became sexually active. I first had sex at 18 but wasn't sexually active until the age of 22.