Not as simple as it should be.
Remove both small oval plastic covers located behind the lights inside the boot to reveal the holes leading to the 10mm nuts.
I used a deep socket with a 6" extension bar.
The nuts are located deep inside the holes and easily fall out of the socket and into the cavity. They cant be recovered so have a few spares handy, i lost 1 nut!
A magnetic socket or some of those magnetic socket inserts would be ideal.
It would be easier to remove all the plastic boot wall linings although these are a bit tricky to get from around the seat bracket area.
Take great care to avoid breaking some of the fixings. The top part of the linings pops off but the base has clips.
Once the 2 nuts are off the light is just held in with a pop off stud at the top so just pull the unit towards you.
The bulbs for the brake light are a twin element T20 type wedge capsule, the indicator being the same type but single element and amber coated.
Again take great care when replacing, over tightening the nuts will pull a big chunk of the lense out and ruin your light.
There is a foam gasket seal which makes the light bouncy when pressed.
I found it best to press the light in and tighten without using the ratchet wrench only turning the extension bar.
Finaly use the ratchet to nip up the nuts to ensure it does not work loose.
Replace the linings and then its job done. EASY???

---------------------------------------------------
Current- 04 Silver YRV TURBO
Past- 91 Black Charade GTti, 89 White Charade GTti, 1998 White 1.3 Hi-Jet.
A friend in need is a friend in deed, a friend always in need, an Effin nuisance!!