Why are new and used cars cheaper in

Bull! Obviously your brothers nissan has issues, no question there. I have two Toyotas, one a 92, a little rust from previous accident damage, easy fix. The other a 98, nothing. So to suggest that all japanese cars have rust issues after 10 years is complete and utter bulldust.
The worst example of rust I work with is an 06 euro built ford, so now I should say that all euros rust before 10 years to use your lack of logic!

1500 Pound for an RX-8, its the proper 231hp model too, not the base model you see here for 10K +

http://www.ebay.co.uk/itm/2005-54-MAZDA-RX-8-4dr-231-/160982878822!pt=Automobiles_UK&hash=item257b53ca66

On the flip side, they want 2495 Pound for an old E30 325i Like mine

A good question, for UK sourced vehicles anyway. Probably the importers making hay while the sun shines. Remember most European cars come from other countries, and the euro hasn't done the same nosedive as the pound.

The Euro has definitely nosedived against the NZ Dollar in the last 4 years.

How old is said sentra!
I have a yard FULL of 10 year old jap cars and NOT ONE has a corrossion issue

Its called scale of economy - not greed. Also, Bizline J Box's are $3 at Ideal Electrical wholesalers , if you are paying $30 for a PDL or whatever J Box you are a fool. Other IP rated J Box's are cheap as chips too.

I got told, the importing of the uk vehicles is very cheap at the moment. Apparently something to do with the milk product moving out of nz ports. backloading maybe! dunno but a prominent car dealer here has a few and was saying. a buyer over there picks the top grade, under 4 year old vehicles, and they get cheap shipping back - cheaper than they can get out of Japan normally.
Anyhow, on to this rust. I worked as panelbeater in 96/97 in Hereford, Midlands, UK. Worked in a commercial vehicle yard. And it assounded me how quickly vehicles were rusting. Some were from prominent salt roads, some not. The popular one that i then saw a lot of back here in NZ was the trusty Tranny. Rear door botoms at 18months, major sill rust at 2 years, I felt they were really built with a ten year lifespan, but am interested how the likes of the VW crafters are getting on with their 12 year corrosion protection. etc. Well, caugh up with old boss a few weeks back, and apparently their not doing too bad!

Yeah - but what does it cost to insure! Thats the issue with sports cars in the UK. I recall the Cosworth Escort being uninsurable for a period due to high amount of claims from crashes, no insurance in the UK, no MOT which makes it illegal to drive. Obviously this restricts buyers.