Some items to perhaps consider for a PSK kit.

BCB Mini Mess Box
http://www.bcbsurvivalusa.com/xcart/catalog/BCB-Mini-Mess-Box-p-16156.html

Caselogic Small Hard Drive Case, EVA Outer, Black
http://www.amazon.co.uk/Caselogic-Small-Drive-Case-Outer/dp/tech-data/B000HDJT4S/ref=de_a_smtd

BCB wire saw.
http://www.bestglide.com/Wire_Saw_Info.html

Compass - Silva Escape & Evasion Compass 40 Luminous
http://www.springfields.co.uk/bush-craft-field-kit/location-aids/compasses-whistles/?id=3148

10 Lifeboat NATO matches plus striker NSN 9920 99 737 1041
http://www.brigadeqm.com/cgi-bin/tame.exe/store/level4c.tam?M5COPY.ctx=31398

Pak-Lite SUPER Glow White LED Flashlight + Ultralife Lithium 9V Cell
http://www.9voltlight.com/inc/sdetail/14555

Fenix LOD AAA cell flashlight
http://www.amazon.com/Fenix-L0D-Level-Performance-Flashlight/dp/B001GAOO9G

Small Boker Subcom copy knife or even the genuine article or space permitting a SAK Forrester
http://www.dealextreme.com/details.dx/sku.19364
http://www.knifecenter.com/kc_new/store_detail.html?s=BO589
http://www.amazon.com/Victorinox-Swiss-Army-Forester-Multitool/dp/B0007QCOTW

Butane Lighter (compact, durable and reliable)
http://www.dealextreme.com/details.dx/sku.16699

Small tube of Vulcanising Rubber Solution (available in commercial bicycle repair kits) such as;
http://www.simpsoncycles.co.uk/product.php?xProd=1898

20-25 metres of Kevlar Tying Thread rapped around a selection of needles (doubles up as a make shift fishing line with some small hooks, snaps swivels and a single small weight etc)
http://www.amazon.com/Kevlar-Thread-Colo...=nosim/kkorg-20

Titanium Whistle (very small)
http://www.uniquetitanium.com/titanium_whistles.htm

Esbit Hexamine 3 x 14gram Solid Fuel Tabs (If container size allows)
http://www.rei.com/product/653344

Titanium Wing Stove
http://www.backpackinglight.com/cgi-bin/backpackinglight/titanium-esbit-wing-stove.html

Small Candle (beeswax impregnated with Citronella) cut down to fit PSK container
http://www.bearcreekcandlecompany.com/becica1.html

Bog Myrtle (natural insect repellent) or even a small block of Bog Myrtle Soap.
http://www.amphora-retail.com/myrtle-essential-10ml-p-237.html
http://www.highlandsoaps.com/cat-9-subcat-17-product-403

ALOKSAK Element Proof Bags (various sizes etc for carrying water, waterproofing gear etc)
http://www.bestglide.com/aloksak_info.html

Alcohol Prep Pads (cleaning wounds and fire lighting)
http://thefactorydepot.com/Acme-United-5...ce=GB&id=uk

Ultimate Survival Starflash Signaling Mirror
http://www.basegear.com/starflash.html

1/3 of a Bahco Bi Metal hack Saw Blade
http://www.amazon.co.uk/Bahco-3906-300-3P-Hacksaw-Blades-12In/dp/B0001IX7YW

Swedish firesteel mini (dump the striker and use the Bahco blade instead)
http://www.rei.com/product/762946

Water Purification and Neutralising Tablets
http://www.justincasesurvival.com/kamiwaputa.html
http://www.gear-zone.co.uk/eshop/Lifesystems-Neutralising-Tablets.html

Small Medical Kit

Codeine Phosphate, Ibuprofen, Aspirin, Imodium, Piriton, Tetracycline (full Course)

Potassium Permanganate.

Surgical Blades, Butterfly sutures, Plasters, 3/8s suture needle etc.

A few sheets of A6 Waterproof paper (write in rain) and a Fisher Space Pen refill wrapped in duct tape

http://www.rvops.co.uk/field-kit-81/waterproof-notepads-70/all-weather-notebook-935t-1723.html

http://www.spacepen.com/refills.aspx

Heatsheets BIVVY SACK Emergency Survival by AMK (space permitting)
http://www.redflarekits.com/pc/1038/rr/Heatsheets+BIVVY+SACK+Emergency+Survival+by+AMK

Mosquito Head Net (again space permitting)
http://www.lifesystems.co.uk/psec/mosquito_nets/mosquito_headnet.htm