The Tokico springs are discontinued. There are UK sources for springs (Faulkners etc).
There are many sellers on eBay and elsewhere doing the bushing kits so choice to shop around there.
The sway bar kit - US cars didn't come with a rear sway bar so their aftermarket kits are designed to mount differently to JDM/Euro/UK etc cars that came with mounting points on the shell. Personally, I'm not convinced you need to replace the standard ones, at least the rear one anyway.
Strut brace - is Moggy240 still making these up? Quite a few of us have the ones he put together. He might have some suggestions on this part.
Radiator - that one is a China-made cheapy most likely, like those you can get on eBay in the UK for 130 quid. Try Mishimoto instead. Several Zs I've seen have them fitted. Look good. Available in the UK for £252:
http://www.mishimoto.co.uk/datsun-240z-performance-aluminium-radiator-70-73.html
Mishimoto also do the hoses in silicon (obviously more expensive than rubber ones)
Front valance - IMO, the urethane ones are not a nice shape and an ugly finish. FRP Automotive do valances but seem totally flaky these days in terms of reliability as a business (I know Craig has had health issues). From MSA, if you want the brake ducts, get the Type 1 ducted version:
http://www.thezstore.com/page/TZS/PROD/classic02a01b/50-1402
I think Type 1 non-ducted looks best (and totally JDM) but I'm biased there!