Technically there is no such thing as a forklift licence in the UK. If you are going to drive a forklift on a public road in the area close to a depot/warehouse then you will need a Category B licence. (Category B is the normal car licence).
So, to use a forklift truck on private property such as a depot/factory/warehouse you do not need to have a driving licence nor do you need to have a provisional driving licence. However you need to ensure that you never need to drive on the public road. At some places of work it may be difficult to tell where the public road ends and the private land begins, so take care.
Although you do not need a DVLA licence to drive a forklift on private property, you do need to have received adequate training and to be able to demonstrate that you have sufficient knowledge and ability to drive the fork truck safely. The type of training that you receive has to be appropriate for the type of fork truck that you are driving.
It is primarily the employer's duty under the Health & Safety at Work Act to ensure that all staff are adequately trained in any type of mechanical equipment that they will use in the course of their work (including forklifts). The certificate that you obtain is often referred to as a forklift licence but in reality it is a training certificate.
It is normally expected that you should renew your training every two years.