Paul Kehoe, the airport CEO, was interviewed on the site and said that it will mean a new road having to be built on stilts across the main car parking area. The cost, to be born by the airport shareholders (as the CEO put it), is said to be many millions of pounds, but the timescale is not known.
Mmm. Actually, I think he means that it will be "funded" by the airport shareholders, but of course, the cost will be "borne" by the airlines using the airport and the passengers that fly on then.
I deal with another Macquarie infrastructure company, and I can tell you that they rub their hands with glee at spending as much as they possibly can in building new infrastructure. Infrastructure expenditure gets capitalised, and the more they spend, the more money they get back from it (typically they charge it back to the business on 8-10% margin). That allows them to put up the fees for using the airport using the the DfT decision as justification. And, of course, there's no lack of demand for Bristol, so chances are they'll get away with above inflation increases, etc.
Mac intensely dislike spending money on operations, which simply hit the bottom line.
I would very much doubt that Bristol (or indeed the Ferroval owned BAA) put up much of a protest at "having" to spend so much money on new infrastructure. Maybe the airlines and passengers should point out to the DfT that their irrational decisions come back to travellers in the form of higher airport taxes?