I think it only lasts 5 years so effectiveness has probably faded now since it was a while back.
Assuming you complete the course of vaccinations, then it is now considered lifetime protection, though there are some who do not respond and produce antibodies, so even from completion of the course they may not be immune and lifetime is therefore not really relevant.
Hepatitis B prevalence is generally low in UK population, so your chances of encountering it are low but this does not apply to other countries and given the nationality demographic of UK providers, this potentially increases the risk within the overall sex work environment. Also should you be exposed the virus is highly virulent and the chances of transmission can be quite high. The virus can also survive outside of the body for longer periods .... vastly longer than HIV.
Since circa 2017 all babies in the UK are now routinely immunised against Hep B as part of the infant vaccination regime so for future generations this potentially will not be an issue.