Rrs supercharged 2007 just under rear bumper two weights that pivot and what looks like two small shock absorbers can someone explain these please

They are called harmonic dampers (the big weights that is!) and their purpose I believe to reduce/ eliminate front/rear pitch. As it is an S/C you also have clever dislocating ARB's under there as part of the Dynamic handling clever tricks. 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

They serviceable ?

Apart from checking the weights swing/slide freely there shouldn't be any maintenance as far as I know. For the trick ARB's look out for hydraulic leaks as it is an electro Hydraulic system. The Dynamic response Hydraulic Oil reservoir is under the bonnet 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

They are tuned mass dampers. They're there to smooth out vibrations/harmonics in the chassis.

https://en.wikipedia.org/wiki/Tuned_mass_damper MY08 RRS TDV6, Chawton/Black, sunroof, hk, 268k km
2001 Audi A4 1.8T quattro 5mt sport, 340k km
1990 Nissan Pintara TRX, lots of mods, 438k km

Also the small what look like mini shock absorbers

The mini shock absorbers are part of the link between the ladder chassis and the monocoque body section. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed