Thank you for an informative post. The plastic guards/inserts seem to be a double-edged sword, being a good protector for the first few years and then being the devil incarnate if not removed and regularly cleaned.
This helps to confirm my view that I will look for a Mk 4, helped by my dear wife extending the budget a little! I would be interested to hear from anyone who has experience of rust issues with a Mark 4. I do appreciate it depends on many things i.e. care, the locality of the car, whether rust protection was applied (interestingly I've not yet seen an LS400 where someone has taken the time to waxoyl the car, unlike many other older cars I've seen or owned.)