A fast-jet hitting a medium-sized bird at 420 kts can sustain a significant amount of damage, due to the v-squared element of the kinetic energy equation The most vulnerable area is the cockpit and it is not unknown for the bird to penetrate the windscreen and cause quite major injuries to the pilot. Aircraft have crashed when the the pilot has been incapacitated in this manner. Even if the pilot is not injured, windscreen/canopy damage can make crew communications very difficult and greatly complicate dealing with any other system malfunctions. A strike on any other part of the airframe is also treated as a significant event and the aircraft will usually divert to the nearest suitable airfield. The aircraft's handling characteristics may be affected by airframe damage so a check of response at approach speed is usually performed at a safe altitude before attempting to land
A great deal of low-flying training takes place in the Northumberland, Cumbria and Scottish Border areas, so an aircraft that has a birdstrike anywhere in that whole region would climb away from the ground and head towards the nearest airfield, which would probably be Newcastle, Leeming or Edinburgh.
In this incident it appears that a bird has broken the canopy, which would have been a very nasty experience for the crew. The subsequent 'excursion' from the runway may have been as a result of a compounding systems failure or due to crew injuries. The fire service may well be referring to the seats and practice bombs when they say it has been 'made safe'.