If i change my Middle name by deed poll, will i HAVE to change my pport immediately?

Well basically im in the UK with a UK pport, my current name is Marlon Jerome Elijah Richards. I would now like to change my middle names to just Marlon Cisse Richards, as a way to remember my best friend who i have recently lost to a car crash. Now if i do this by Deed Poll, would i urgently need to send my pport for a change instantly or will i be able to just leave my pport as it is Marlon Jerome Elijah Richards, the main thing stopping me from changing my pport is the cost and hle of making amendments to my passport. Thanks, please URGENT ANSWERS QUICK