Recently also did some of the renovation works for my 5 room HDB flat. I also not sure what interior design firms are good and dont want to be ripped off. One of my friends recommended me to Singapore carpentry firm. They did my kitchen cabinets, design new walk-in wardrobe for my master bedroom. Now just finish. Overall, quite pleased with their service and workmanship. Hope this helps other who also renovating and designing home. P.S. Can PM me if you want to see pictures of my finished kitchen and wardrobe