I'm yet to hear (ie, not hearsay but from the affected person or their immediate cohort) of a case in either the UK, NZ or Australia, where an insurer declined a claim, or a driver was prosecuted based on
either a minor modification (eg, non-standard wheels/tyres/lighting) or a minor defect (eg, underthickness rotors).
In cases where such items are cited, there always seem to be aggravating factors such as speed, drunkenness, road rage. Even when there is a question mark over such possibilities, it's very rare for (say) airbag data dumps to be tendered as evidence - even in an inquest. Submissions usually focus on traditional evidence such as length of skid marks or eyewitness accounts. The times when a vehicle is gone over with a fine toothed comb, are usually when someone is trying to (shiftily) blame the car for a deliberate act of their own - such as saying the throttle stuck or the steering locked, causing them to run over their spouse...
As a road user, I prefer to share it with people who drive or ride knowing the present state and limitations of their vehicle, rather than people who may have a 100% "legal" car but drive like blind zombies, warm in the knowledge that their insurance cocoon will protect them if they stuff it up for others.
A worn rear beam on the Berlingo takes some of the fun out of piloting it - mine is clunky and needs new pins, Neat have currently none in stock and the Lithuanians want a small ransom (£65) to post me a pair: http://manodalys.lt/product.php?id_product=1071260121
Post to England is much more amenable.