I hope I may offer a couple of suggestions. I live on the other side of the globe and we also have these elusive little kingfishers.
Though a different species.
Alcedo azurea is the one that is similar to your UK species.
1) Find a good perch that you can set up along the flyways where you often see these birds. By good perch I mean a nice color, shape and perhaps even some pretty lichen growing on it. You can make a base for it similar to what I have just done and I went about by using a small (5-liter) bucket and placed a large dog food can in the center and poured quick-set concrete in leaving the can open with concrete on the sides holding it down.
2) Get a smaller can (any can) that fits just inside the large one (I have a good supply of cans as we have six cats, two dogs) and put your perch in it and pour the concrete into this small can. When it sets, you can slide it into the can concreted into the bucket.
So you can make a few perch set-ups cheaply and exchange them so that your perches don't look boring and the same in every image. Just make sure the perch is almost bent to 90-degrees so you have an upright trunk then the perch off to the side!
3) Get a small net and catch some of the small fish that the kingifisher would live on and put them into the bucket under your perch that you had set up. Make sure the lip of the bucket is about 5cm above the water level or the fish will swim out!
4) Sooner or later your kingfisher will find this as you are already in your little hide waiting and should get some marvellous opportunities.
I read about the fish bait trick in a British Wildlife photographer's book - cannot remember the title. Sorry. The essence of the tip is there.
Here is a link to one of my iamges of our Azure Kingfishers in Australia, they are about 18cm long. rather small. this was a lucky capture, no hide was used, I was allowed to walk to about 7m away as it perched by my local river.
www.ausphotography.net.au