Seventy quid for a 70 mile Journey??? When did you last take a taxi that length in the UK?
I get a taxi to GLA regularly & I'm mid-£60's each way for a 40 mile journey, less if I'm able to book the return. As with all things the further ahead you can book, the less it will cost.
Having said that, a few years ago, I did get to use the Emirates chauffeur service a few times when I was headed for south east Asian jobs & each time the drivers said to me at pick up "Please do not tip me Sir, It is Company policy that we are well paid for our services and no tip is needed".
One of the guys I knew quite well from having picked me up through another chauffeur service told me that Emirates took the view that unless you intended to tip everyone from the chauffeur through desk agent, cabin crew, flight crew, arrivals agent and arrival chauffeur, it wasn't fair to the people serving your flight that you couldn't tip e.g. ground crew, baggage handlers etc.- so to avoid any feeling of injustice among staff and core contractors they would operate a Tip All or Tip None policy and as some couldn't be tipped it would be tip none. This may have changed, but it certainly seemed to be in operation everywhere I was fortunate enough to use the service, but as I said, it's been a few years.