In the UK there are a lot of Japanese cars, and thus a lot of Celicas, in the rest of Europe they are not as common, the Facelift here in The Netherlands is pretty rare, the majority of them are 99-00 models, and most of them are in grey. after 2002 the sales of the Celica dropped and even the Facelift couldn't prevent that. if I'm not mistaken in 2005 there where only 100 or so Celicas sold over here.
The good thing about the Interior is that you can easily change the seatcovers and replace them with leather version.
Same goes for the rear seats (which isn't real leather btw, but he how often do you sit there

)
So shipping the leather parts isn't that much of a problem so buying them oversees doesn't have to be very expensive.
Check the UK ebay (
http://www.ebay.co.uk) they often have Celica stuff for sale including facelift parts and leather etc.
The facelift leather is also different from the pre-facelift, facelift is perforated leather where the pre-facelift is not.
There where also several different versions of leather seats sold in Europe and in the UK specific, like 2 tone versions like a special T-sport version (see below) and Alcantara/leather version.
I'm thinking of replacing mine with the T-sport version like this one:
I found a new set on Ebay a while back but missed it
ooh as for plans, there are some plans, basicly the exhaust system upgrade with a new manifold and race cat and smoother midsection, and I can get a Blitz intake from a mate, who is stipping all modified and performance parts of his track prepared Celica and returning it to stock., he btw has a set of facelift lights that will be sold also, but they often go for 150 euro here also.