Kona softens up a bit and the weave tightens once it's washed. You may want to try that before you order anything to replace it. It may make enough of a difference for you.
As for other choices, Moda Bella has a softer hand than Kona solids, but it's still a broadcloth (60 square thread count). RJR Supreme Solids are very close to regular quilting cotton in weight and hand, with a large choice in colors. I do not know the exact thread count, but I recently discovered this line and like it a lot. I'm sure it would be available in the UK.
http://www.rjrfabrics.com/fabrics/co...packageID=1007
I'd try pre-washing the Kona you have before you make any further decisions. Bird in the hand, yes?