Hi Stephen,
I read with interest your plans for a Mini / mini cooper S.
So far from the responses I see there's already a lot of misinformation !!!

.
Try the site below for good information.
http://www.ozcooper.com.au/new_page_3.htm
My other hobby is Mini's, and they are great car if properly maintained .
If you are confident of doing most repairs yourself you will save a fortune.
Try and find work shop manuals, don't buy a Mini without one.
Below are my current mini's
1968 Black and white mini deluxe and 1975 mini S red.
My current project 1963 - 850. in under coat.
My first mini, 1963- 850
My 50th birthday, my wife made the Italian job Cake

. The other mini in the image is my brothers Cooper S replica.
BTW there's a lot of replica's around passing themselves off as original, the site I supplied will you where to look for the correct body and engine numbers.
Some things to know, there's nothing wrong with hydrolastic suspension, you can get new units, I made my own pump to keep it pumped up.
There's no such animal as an 1800cc mini!
Not unless it was transplanted out of an Austin 1800 with a lot of modification.
Do not go down the road of trying to transplant a Honda a Corolla motor.
Yes it's done.
But to get it passed for road use will cost you a fortune.
If you PM me I'll supply some names and more info if you want.
Cheers,
Justin.