ok have searched for an answer but to no prevail, i have the error code either 5 or s flashing on the trip computer i can reset the trip computer but have to do it again once the car is turned off and started again looking for uick response too pls.

i assume youved disconnected the battery. you need to tell the trip comp. if its sedan (s) or wagon (w) and then 3ltr or 3.5. i think you press the mode to enter and up to change between them

so i have to disconnect teh battry to enter the trip computer settings

No, it is asking you to enter the settings using the mode and arrow buttons, it will ask you for "S"sedan or "UU" Wagon and it will ask "3" for 3.0 litre engine or "3.5" for 3.5 litre engine. It must have been reset recently, wether from a bettery disconnect or some other means.

No, once you disconnect the battery the trip computer resets
Hold the two arrow buttons untill it beeps, then do it once more
The key needs to be either in the ACC or ON position to work
Should be clear after doing the above :)

have you lost interior lights and/or central locking?
check 1 (15 amp) of the 2 fuses in yellow enclosure in under bonnet fuse box.
blown fuse will stop trip comp from retaining settings too.
happened to me on weekend (thanks mightymag for ID'ing problem)