OK, well I ended up attempting it but didn't rehydrate the cells. Instead I triple cycled (0-100%) each module, typical capacity before was 2500mah but after the cycle, over 4000mah. Vast improvement!
I couldn't bring back one module, looks like a cell had reversed and couldn't get over 6.7V, although capacity was good. I assume this was across the remaining good cells.
I bought Prius Gen 2 modules and fully tested (cost of £30). I can report that it fits the Lexus module specs EXACTLY. Don't be fooled into thinking the modules are different, they are not!
New module fitted and put the car back together, drives absolutely spot on! Averaging 33-34mpg and I am quite generous with my right foot :)
Now to improve handling using Tanabe NF210 springs!