GPs do not provide an occupational health service as part of their NHS responsibility nor can they provide this service to you even if it is funded by you.
Under Health and Safety Regulations, your employer has a duty to provide a safe working environment and, therefore, appropriate health advice for those at risk of infection with Hepatitis B. We advise you to contact your employer who will be able to make arrangements with an occupational health provider for the provision of any immunisation which you may require following an appropriate assessment of the risk to which you are exposed.