Many parts shops sell refurbished original Kia calipers from name brand manufacturers such as TRW and Budweg. You get about 30 pounds back later, when you deliver your old caliper.
I paid about 99 pounds recently, +30 deposit.
A new Ridex caliper may be about 50 pounds. I have only ever installed 1, about 4 years ago, and it is still functioning OK.