Universal Flush Valve - Water running into toilet?

Hi, I have a very small toilet in an en-suite which has one of these Universal Flush Valves. There is no ball-cock and it is not that obvious how it works. It takes an age to refill the cystern and constantly runs water into the toilet bowl between flushes. It has become such a nuisance to use that I am considering removing it but would be grateful for some advice.