Any driving from your LHR gateway to the airport (Farnboro, Luton, Stansted, Cambridge, Gatwick, etc) where the company aircraft is, or to a different airport to catch an airline, is provided by a contracted limo/minibus company - or taxi for one or 2 (short distance) journeys from LHR.
Obviously, if the company aircraft is at MAN or EDI, & your gateway is LHR, then an airline would be arranged.