Nothing on the SERCO Careers website to suggest that such vacancies exist.
Not sure why but a number of SERCO vacancies have appeared at Chester (Hawarden) , ground manouvering officer, ATC Assistants, and Senior ATCOs.
There is generally only one Senior ATCO at any one unit (unless he/she is the only ATCO on watch). What is a "Ground Manouvering Officer"?
Such a lack of basic knowledge leads me to suspect that there is a Troll at work.