Wouldn't be surprised if the TC relocation brings EGHI into the fold. They and farnboring are currently the only sarf of england NATS airports to run their own approach. I suspect it makes sense from a manpower point of view to have a big melting pot of approach controllers in the one place. I think the chances of HH being involved are significantly less due to the obvious already mentioned and that of radar coverage. The watchman in use at HI has some poor coverage over bournemouth way (or at least it used to !)