Yes, unfortunately do have to spend into thousands on credit card.
Amex has introductory offers, I think the BA card needs a £1000 spend within three months for 10000 miles - that will get you either two europe trips for £17 or four for about £30. You do then collect as you spend, but it comes out as thousands to make a further difference.
I also just put absolutely everything on the card, including the trip.
For me I can book flights last minute no fuss. I once missed a flight at London City, I was there in lots of time so got distracted by whatever I was doing and there are no announcements there, so I realised last minute and rushed but was too late. I literally saw them take my bag off the plane lol!
I went on the wifi, put myself on the next flight an hour and a half later, it was the same gate same place same everything, cost me £20 instead of the £300 it would have cost to get home otherwise.
I've also booked a flight in the car on the way to the airport:)
AirFrance (plus all their partner airlines), it's how far you go/how many flights you take. Can only use your own, not everyone in your group you've paid for unfortunately, but if you do two reasonable long trips a year you will have more than enough to be up to making the experience a bit more comfy.
I agree with the not worth it for short haul flights, unless you want the extra baggage or have so many hours in the airport that you'd like to use the lounge and play the how much free food can I eat/free booze can I drink/how many magazines in languages I don't speak can I collect and how many mini cans of diet coke can I hide in my handbag and still seem classy on the outside. 22 is my record:)