On a better note, I managed to repair the toilet all by myself! I made a call to the plumber but he was busy on a job and told me I had to wait till next week. I decided to dig into the cistern and took out some items which were the apparent cause of the overflowing. I brought them to the hardware stall and found out I could replace the whole cistern fill valve myself...if I could just remove the existing one rooted inside.
Determined to get it accomplished and save time and money, I heaved and hauled, trying to unscrew the ridiculously tight plastic screw at the base of the existing cistern valve (after all, it had been there for years!). In the end, I realised that the proper way for a plumber to do repairs is to remove the entire cistern and lay it flat on the ground. Droplets of sweat later, I had a new cistern fill valve and a well-working toilet again! Total cost = $23.50 including one pair of pliers. Ureshii!
