Bagso
I don't know the specifics of the bond issue but I think you will find that these funds are part of a wider refinancing of MAG's borrowings. It is quite normal that when a company acquires a new asset (eg MAG buying Stansted) the immediate source of funds - such as short-term bank borrowings - are replaced fairly quickly with a longer-term facility. A bond issue - which basically fixes the interest rate for a longish period - is a common way of doing this.
Nothing to get excited about.
Edit - see below
MAG lands in the bond market
Manchester Airport Group inaugurated its new £5bn debt programme with a 20-year bond issue, refinancing half of the term loan it used during its acquisition of London Stansted airport last year. This deal establishes it in the capital markets, and gives it the flexibility of funding options other UK corporates enjoy.
IFR 2019 8 February to 14 February 2014