To change a rear cluster bulb is easy but awkward...
NB there are reversing lights both sides, so you need two LED bulbs as specified in post 1 above, about £8.50 each plus £3 p+p, they came quickly.
You have to remove two oval plastic covers, they come off easily with a small screwdriver. You then need a longish nut driver, as the two 10mm bolt heads are quite deep behind the plastic trim. So about 6" long is needed to reach the upper one. I needed a torch to see the bolt head and get the driver guided onto it.
The two bolts undo easily, though about 20 turns needed. One dropped down but was caught by the bottom of the recess ok.
The plastic housing then pulls straight back. I didn't bother disconnecting the wiring loom, just 1/8 turn released the bulb holder. I put the LED bulb in, left it hanging outside the car wing, and put the plastic light unit partially back. I needed to check the bulb lit up when in reverse, and with only me at home, i needed to see the light in the door mirror. It lit up (I think if it was 180 deg turned in the housing it wouldn't light up) so I put it back into the light unit and 1/8 turn locked it.
I then put the light housing back which took several goes as it has to allign with a plastic bracket.
So that I could guide the bolts in, 6" deep into the housing, I put blue tack on the bolt head to hold it to the socket driver. Guiding it to the hole with a torch, it went in easily.
I only did one, so I could compare the LED with the old bulb, there is a big difference as you can see above. To do the other one will take about 10 mins now I know how to do it.
I won't bother changing the brake or indicator bulbs, they are fine as halogen. The brakes are on when stationary with autohold so dazzling enough anyway, and the indicators are ok as they are.
