No airfield is going to fund your courses or offer you employment, you have to make the commitment to funding and passing then you might just get somewhere.
But if you are already employed at an airfield as an assistant or even as a FISO where the aerodrome also provides an ATC service then there is a chance they will sponsor you through an ADI course, after a couple of years employment. There is however the point of whether you are being employed as an assistant on a long-term basis, or are just looking at it as a stepping stone to getting them to pay for your training to become a controller. It also depends on each aerodromes staffing requirements/budget etc. I do know at least two examples of where this has happened although there doesnt seem to be a great deal of job vacancies in this field at the moment so it could be a rather onerous task!