Allowing for different measuring profiles in Britain as opposed to here in the U.S., a reading of 3.0 to 5.5 PSA serum ng/ml would rasie serious concerns. Are you sure you have the right numbers?
Additionally, you don't say how old you are. Several screens have been done here in the U.S. and indicated that nearly 75% of men over the age of 75 have prostate cancer. The theory has developed that, except with the more aggressive types of PSA, the slowness of develpment is best ignored in older men.
If you have concerns you should ask for an additional test called the "Free to Total" PSA. This is a ratio, expressed as a percent. Much of the PSA in the blood is bound to protein, including that produced by cancer cells. But men with benign prostate enlargement have higher levels of free (unbound) PSA and so a higher Free to Total ratio. If the total PSA level is abnormal, the Free to Total PSA ratio will give an idea of whether the rise is due to benign disease or cancer. Cancer is more likely if the Free to Total percentage is below 10%. (Source: Prostate Health). This a relative benign test using only drawn blood... Best of luck!