Many local authorities provide a range of activities during the summer holidays and there are a number of summer schools offering various musical workshops to children so I would imagine that you would need to start with those first.
The best scenario would be to find one of these organisations prepared to hire you for the six weeks holiday, and preferably somewhere pleasant (Lake District?) but I think you would need to be offering something pretty special as local authority budgets are tight on this sort of give-away activity.
I suspect that Leadfingers is right about the work permit.
One of the members of my band is a school headmaster and was recently describing a visit their school made to see an aboriginal didgereedoo? player. I know that the performer was paid by the education board and any of the schools in the area could attend but this happened during term time.
If I can find out any relevant information that might be of help from my friend I'll pass it on to you.
Good luck.
C-flat.