For changing the toilet seat and basin in the toilets, you can try contacting a plumber. Ask your friends if they know any good plumber or you can call the Singapore Plumber Society. They will direct a plumber based in your area to come over. The plumber will call you and you can negotiate the price. I have used their plumber two years ago, so far no problem but you may not be in the same area as me. They have a price list for reference: http://www.plumbing.org.sg/home_plumbing_service.htm or you can also check with your town council website, under handyman services. They tender contract with contractors who do plumbing, electrical & building works. I have used the contractors in my town council to do some electrical works like replace new 13 amp power supply sockets, install 15 amp socket for aircon. Prices are reasonable but I think you still can negotiate.