OK! update. I received the used replacement rear light for my Lexus RX300 and a good point was it still had the bulb and fittings in so i could practice removing them. I gave to be honest I was not looking forward to this job. I started off removing the panel in the back of the car but struggled to remove the bulb fittings, especially the one right out of sight, didn't have enough strength in my fingers to turn it. Eventually got them all out and started to release the 3 nuts only to find 2 were 6MM and 10mm so more aggro. I think Lexus made this job very difficult on purpose so they can charge a fortune for doing it. So with a small spanner, because a socket was not possible on 2 of the nuts I managed to get them off without dropping any. Replacing was a little easier because of lessons learnt but still very difficult because of needing to get the nuts tight enough. So after a few cut knuckles finally back inn now all I needed was to find it didn't work, because it is impossible to connect up before fitting. Eureka, all works. If I am ever faced with this job again I will scrap the car instead. Used light in great condition, good value at £65, still not sure how one would exchange the circuit board though.
Any way thanks everyone for your help and encouragement.
Stay safe