awt2003

hi there wonder if anyone can help me here, have a 2001 saxo desire diesel which is being a bit of a pest, there is a burring noise coming from the car when accelerating heavy and at about 50mph, i had the driver side cv gaiter replaced at the mot at the end of june and i think it has something to do with that but not sure. i dont think its the engine as the noise does not fade when chaninging gear or dipping the clutch. any ideas of what it could be peeps and if so a ball park figure to get it sorted? another thing does anyone have problems selecting first and second gear at all??? cannot seem to get them some times and ive been told its not the selector at fault, its coming up for a service also, shall it need the timing belt looked at as its nearly 40k its done now?? and again a price for this if anyone knows? ta much tony