if his got a JDM Civic then i suggest you give this site a run through.
now there is no need to go any where else to find help on buildin' that civic!
if not then as you already know, JDM is the japanese market of the cars. domestic market sorry lol. the cars may look ugly but a heck load of parts are available!
Recaro seats don't come in different forms. you have ranges and sorts as each seat is built for a different purpose. the ranges cover from sports seats, motorsport seats, rally seats, bucket seats, pro driving seats and race shells. plenty of choice as you can see. i am sure that you can get seats for any model of the 2-door civic's but you might have problems findin' some if it's a 4-door which i belive isn't lol still there are some available for the 4-door civic but you don' have much choice.
as for your thrid question, jus' visit the link above and every thing you need will be there from help buildin' the civic, help chosin' the parts and plenty more.
Luke, try the link too since you got a civic cambridgeshir boy