How do I learn to enjoy walking - and walk more?

Let's face it, I have become lazy. Too ready to take the car for the shortest distances, happier with a book or dozing instead of being out in the open air, and frankly, overweight. I am healthy, but unfit.
Too easy to blame Paw who can barely walk across the room, but even before his recent illness could only walk VERY slowly and short distances..
Even a new young dog hasn't done the trick, you have probably all seen the pics of Hattie in her favourite position!
I have just come back from a 40 minute walk up to the edge of the village and just a couple of years ago would EASILY have covered twice the distance and not necessarily in twice the time.
So, a training schedule please.
The more I do, the more I am sure it will become pleasurable again and if you ENJOY doing something it is easier to motivate yourself. But at the moment when friends suggest we walk our dogs together I am too quick,to make excuses, mostly because I will be out of puff within 10 minutes.
(Don't suggest walking groups please, I know they would be great but I can't plan organised activity at present. ).