Accessories - first thing is brake controller of course (think I'll stick with my HR one), and roof rails/bars (ebay LR copies for about $450 - any thoughts?). Thinking about a bull bar (LR one?) - planning a lap of Oz in 2015, so will want one for that, and probably change the tyres then (and wheels to 18"?).
With the roof rails, there has been talk of some of the ebay ones being a problem with the glass roofs - apparantly the OEM ones have a small bend in them, where as the china ones don't. They then put pressure on the glass. Some are now marked as "not for glass roof models". Not sure if the British ones are the same. My OEM 3/4 length ones were about $650.
Try LRPARTS.COM instead and ship from England - $AU340 plus shipping
http://www.lrparts.net/genuine-long-version-roof-rails-in-black-finish-for-discovery-3-and-4.html
Bullbars -
Have you seen a genuine LR bar yet? I don't think they're as good as a steel bar. They're very bulky and sit fairly close to the body so I question whether they'd still transfer any impact in the car still, whereas an ARB or OL etc sit further off and offer better protection. Plus they're hugely expensive.
ARB - $2500 ish fitted, Australian made, solid well proven, colour codes available, but not good with the forward camera and sensors, 15mm gap between top of bar and underside of headlights (fit a rubber strip to hide)
Opp Lock - about same price, Thai made, colour codes, made with cutouts for cameras and sensors, same gap
ECB - $?, black, silver, grey or polished, alloy, holes for sensors but not sure about cameras
If going to 18", but a larger tyre size apparently the larger tyre rubs on the ARB bar where the windscreen washer bottle is, whereas the OL one doesn't.
For the 18" rims talk to Gordon at GOE Australia in WA. (also for bash plates, suspension upgrades/rods, driver training/manuals)
http://www.greenovalexperience.com/
Rims are around the $500ea mark, plus probably a few hundred more for shipping cost. But the options for tyres are better.
Also talk to Tim at Traxide for a dual battery kit - made to suit a D4 perfectly.
http://www.traxide.com.au/complete-diy-dual-battery/land-rover-dbs-kits/discovery-4-dbs-kits/
(when I saw talk to them, do just that - they are very helpful and willing to actually talk and explain stuff as necessary)
and if not already with the Freelander, get on AULRO.com (of which Tim, Gordon and the previous referred to Sneigy are regular contributors since they are also LR drivers and appreciators)