RE spoiler, contact Stuart for one of his. Ultra light and perfectly molded and finished. Of course knock-off Porsche Part but 100% same less the third brake light.
Porsche Boxster Spoiler | eBay
RE Speedster hump. Again, not far from you:
Porsche Boxster & Boxster S 986 Speedster Humps | eBay
RE skirts and others, talk to these same guys about what you exactly need and they will find it in a flash for you. Brand new or second hand. Got a few mates currently dealing with those guys at the minute and they are having a laugh I've heard last weekend. No rip-off
If you ask me, Stuart is pretty switched on so you might want to start there
A place closer to you might be the Boxa.net forum. Based in the UK. They have a great classified for second hand parts.