Whenever I close the tailgate the upper tailgate microswitch falls out and is loose when pushed back in.

Are these held in just by the plastic tabs on the side? Or is there another fixing that should be there and has snapped off?

Also the tailgate is very heavy to open? Is this common on the 2007 sport or a sign that the tailgate lifting arms are worn?

The tailgate microswitch is secured by the 2 plastic moulded tabs - nothing else - if you ever need to remove it - the safest way is to remove the trim ( 8 torx screws ) & release from inside - I found out the hard way & broke a tab - had to replace the whole switch ( it was corroded anyway ) £28 to replace from a stealer As for the arms mine is very light to lift.  16MY Estoril Blue SVR.............
17MY Autobiography Dynamic - Corris Grey - WOW.
14MY Autobiography Dynamic - SDV6 - Fuji White
12MY Autobiography - SDV6 - Santorini Black - Dual View - Rear Entertainment - Sunroof.
12MY Autobiography - SDV6 - Orkney Grey - awesome ;(
2005 Java Black - 4.2 V8 Supercharged First Edition- will never be forgotten ;(

ive only had it 2 days, so ive bitched to stratstone to have the problem sorted.

i might have the tailgate checked then, because my mrs has to use BOTH arms if she wants to open/close the tailgate. and even i dont open and close it with much ease so will get it checked.

im wondering if the hydrolic arms are worn and not assisting as they should be...

After this short a period of ownership get the 'hydraulic" units changed along with the switch under their warranty !!

Pressure in the support arms should be sufficient that it should almost rise on its own - if they argue "its normal" ask to try one of their other cars