Thanks for all the help here.
Got the fuse (and some spares) but was unable to get the old fuse out using the fuse popper bought from Halfords. It seems Lexus have spaced them so tight that the tool does not go between two fuses to extract. Had to then go back and buy the smallest needle nosed pliers I could find. Even then it would not go in between the fuses but did somehow manage to get it out. It would seem that using pliers does cause a bit of damage to the micro fuse top. Once new fuse installed, all is well: aircon dash working and the srs warning notice gone. Thanks again.
How to others take out the fuse on the Is300h? Specific tool would be greatly appreciated.