benefits of changing engine mountings

i have a skoda fabia vrs tdi 130 54 plate 60 k on the clock have had some serious work done on it in the past head gasket including skimm and repair cambelt water pump. im a little concerned about the economy struggling to get 50 mpg on a run down the motorway i believe i have a worn engine mounting on the rear and was thinking that if it was changed would it make the engine run smoother and more economical i have noticed i freind of mine has the same car a little more miles 73ish his car on start up it seems smoother and the intial pull away seems smoother too not sure weather by changing the engine mount on my car will make any difference to economy or smoothness i maybe wrong but i have noticed that there is a little more than normal movement in the engine back and forth not side to side i believe to change this rear mount isnt a too bad job any one reading this with any help would be great one skoda furby to another