Removing and using programmed Atmega 328 of Arduino UNO on customised PCB I am a newbie. I would like to kno whether the original Atmega328 on Arduino Uno, programmed with my own sketch, can be removed from an Arduino Uno board and used  on my customised PCB?
Yes, it can. Your board will need to provide +5v and ground, a reset signal, and a crystal for the chip's programmed clock frequency (unless you reprogrammed it to use its internal clock). The power and clock signals will need filter capacitors. You can even re-program it on the board with an FTDI (USB-TTL Serial) cable. 

There are lots do-it-yourself instructions to build an Arduino board, which is a good place to start, even if what you eventually want is a larger system board with an Arduino integrated into it. This is one I can vouch for; I built Mr. Alves' Version-1 as my only Uno-like board and have been using it for several years.