My company policy is that I can book any flight that is within £100 of the cheapest direct economy option. I think that is about right and is what I would do if it it were my own money. I speak as someone who lives 25 minutes from Heathrow though, if I were nearer Luton or Stansted I might not judge BA's frills plus a longer/more expensive taxi ride as £100 better than EasyJet.