if you are struck off it means you can't practice AT ALL as a doctor, not just not working for the NHS. You are struck off as a doctor. Anyway, as above - the whole range of careers and jobs that do not entail you haveing to be a registered doctor
it depends on what the gp was struck off for - was there a criminal offence involved - if so nothing where they need a clear record - which is a lot these days.
baileybird is correct. It does indeed depend on the nature of the offence, but they can work for government agencies such as DVLA where they are able to provide an opinion on whether someone should be allowed to drive.
The reality is that no matter what they've done their ability to give a medical opinion remains unaffected. It's a common misconception that struck off doctors end up doing unskilled work..