2003 Rover 100 car spits &jumps nearly cutting out

Is it missfiring,sounds like it with your description,could be a fouled/partially shut spark plug.maybe a starting point to remove and check the plugs,see if theres any difference in them,and get the codes read to see if any possibles logged.These cars are quite notorious for cylinder head problems,gaskets,cracked heads.if they have been run too hot.However i would start with the basics and try and locate the fault to a cylinder.