Working on Great Britain should be no more difficult than working in the rest of the United Kingdom. How united are you really when you have seperate rules for work depending on the zip code? The United Arab Emirates does not have such restrictions. They are very successful. The United States only requires that the taxes be paid to the State. Aside from that, work is work regardless of the region within the nation.
If you live in the UK--in any part of the UK--you should be entitled to work in the UK and Britain, considering that the only country not considered Britain is northern Ireland. But who cares. This is a silly question as both the UK and Britain are basically one and the same.
I believe people should be entitled to work both in the UK and Britain. Given the small area I do see a problem with allowing this because it gives people more opportunity. I do not believe people should be restricted based on where they live when considering employment. People should have equal opportunities.
A person should be able to choose to work, so long as there is work to be done and the individual is properly skilled in the work. If this work follows local laws and does not adversely affect a large number of people or the environment, there is no reason to prohibit them from working in both the UK and Britain.
Great Britain led the world in abolishing the institution of slavery (which is the entitlement to the resources and labor of other people) and it is extremely short-sighted to refer to things like "work" and "labor" as something one has a right to. It is a distinctly humanist concept to believe that all people have the right to their labor and the fruits thereof (salary or profit). Slavery should remain, in any form, illegal.