Most common cause of ABS and Skid lights coming on seems to be one of the wheel speed sensors going faulty.
Without looking at sensor data (can Carista give you a view of the raw wheel speed data?) to see which sensor is failing, your cheapest option would be to buy one left and one right side sensor and change one sensor at a time and check to see if that cures the fault. (If changing the sensor doesn’t fix it, put the original back and move on to the next one with the new sensor used to test there. The sensors are handed so you’ll need a left and a right version)
Visiting a garage looks to cost around £150 for a repair, while sensors can be bought for £15 to £45 each and they are an easy fix if you have the tools and inclination to change them.