Oh for Gawd's sake, why all this antipathy towards the NOTA? The Irish now have a radar that looks out over that bit of airspace and we would be failing the aviation community, who after all pay for the service, if we prevented them from using it simply to protect a few theoretical jobs. As for revenue, Shannon would have to be giving some pretty bizarre routings for aircraft to avoid UK airspace.
And anyway, it isn't 'our' airspace to give. Shanwick's airspace is international and it is up to ICAO who provides the air traffic services within it. In fact the Irish could legitimately tear up the Shanwick agreement in a couple of years and put a case to ICAO for them, and them alone, to provide ATS within the Shanwick area. And that would NOT be good news for real ATC jobs in the west of Scotland.