Fire Lighters:

Always have more than one method of lighting fire. Waterproof, strike anywhere matches stored in a 35mm film container, disposable "Bic" type lighters and Flint & Steel are all worth carrying. Cotton wool balls soaked in petroleum jelly and stored in a 35mm film container only need a spark before they ignite, the petroleum jelly enables their use even in wet conditions.

Map:

Always carry a good OS map of the area you will be visiting, 1:50000 or better still 1:25000 series if available.

Compass:

Purchase the best you can afford and learn how to use it. GPS systems are great but only as long as the batteries last.

First Aid Kit:

A good FAK is essential and should contain at least the follow: plasters, painkillers, blister kit, small & large wound dressings, safety pins, sterile wipes and any prescribed meds you may take.

Water:

Look to carry at least 2L of drinking water though this obviously depends on your climate. Boiling water may enable it to be drinkable but you are advised to research what resources are available in your area. It goes without saying that you should always use the cleanist water available. Puritabs also remove dangerous bacteria from water but will not remove chemicals, heavy metal contaminents etc. A good water filter that removes all threats would certainly be an excellent choice.

Tools:

Purchase a decent quality knife and multi-tool. Knifes should either be fixed blade or locking and kept sharp.

Communication:

Do not dismiss the mobile phone, much of the UK has 98% coverage. Additionally, carry a whistle to signal for help. 6 sharp blasts.

Torch:

Carry a decent quality LED torch and spare batteries along with a LED Head Lamp.

Shelter:

Depending on where you are or your individual requirements, bivvy bag, tarp/basher or tent.

Your brain!

Your brain is your most important piece of kit, being mentally prepared, learning how to use your equipment correctly and common sense will give you the edge you need to survive.