The definitive guide is here:
http://www.dft.gov.uk/vosa/repository/MOT Inspection Manual.pdf
Now on reading this there is the guidance of a switch being present and working. This is clearly required for a switched circuit but begs the question what happens/is applicable to waht you are asking.
I would say that "if it is fitted/present it has to work". So if you have a floppy sunvisor that won't stay up you can legitimately remove it for the MOT. If you can remove the switching circuits/controls for the sidelights/dipped headlamps without affecting any other function then I suspect you wil be perfectly OK. If the lamps come on because the switching controls are defective then you will fail.
I'm not an MOT tester, just applying sensible logic to the "offical manual". Besides the "MOT manual" there are also many bullentins issued to clarify all sorts of issues.
If you want a pretty defintive answer then go to you local council MOT testing station, usually located at the council workshops. They are totally impartial, make no money except the test fee and will always give you correct and sound advice. If your local station is 'normal' (like mine) then they will also provide quick free specific tests where such tests are beyond the scope and/or require equipment that joe public hasn't got.
What does this mean in reality. Quite simply you can take a single testing issue, like headlamp alignment, brake test, emission test etc. to them and they will, as part of their public service to ensure people have safe and clean cars, test or comment on that single issue.
If you want to do this then phone them to arrange a convenient time and be prepared to accomodate their timings and not yours.
