I have a Scenic 2001 and the engine keep cutting out when stopped or at very slow speeds. Very annoying when at traffic lights. took to garage today could find no fault said it might be top dead centre sensor but very difficult to change and would cost £198,from reading these posts I presume this is totally wrong and quite simple to change. Is this right??
It probably is the Top Dead Sensor - you have the same symptoms as I did.
I would refer you to my posting above yours where I did the same thing on my 2000 scenic. I personally would not tackle it again despite you saying it costing £198 to fit a £20 sensor. I can well imagine it taking at least a couple of hours for a mechanic to disassemble/re-assemble all of the bits required for access to do the job properly - and not to end up with shredded fingers - the way I finally ended up doing it.
In summary - it is just about do-able but it requires patience, dexterity and the ability to work without actually seeing what your doing. It's a pig on a scenic because the sensor has to go at the back of the sensor mount (that you can't get to) and not the front.
Hope this helps.