We have a KDL-26U2000, the problem is the menu button doesn't bring up the menu?? When you press the button on the remote or the top of the tv the green light will flash so the tv must recognise that I'm pressing it but nothing happens? I've tried to reset to factory settings but when I've got into the service menu I can't input anything? Please can anyone help??

Checking your remote can be done with any digital camera since they can 'see' the infrared light from them but I suspect the remote is working; generally, if they are emitting anything, it will be sending correct correct pulse trains.
Having the camera 'live' you will be able to see that the remote is working by aiming the remote at the camera's lens and pressing any button while watching the camera's LCD display. The output of the remote will appear as white or near white blinking lights.
> I've tried to reset to factory settings but when I've got into the service menu I can't input anything?
Often the service settings require entering some code (password) sequence to access factory settings and it may not be possible to enter the code if one or the other end of the IR system isn't functioning.
Summary; I think the remote transmitter is OK but the receiver in the set is not decoding the received signal despite it indicating that something was received.
I think the set itself is a fault and you will need a tech on site on in the shop to search for the right board to replace since the IR receiver may be part of the main board (expensive) or a separate assembly (somewhat less expensive).