Compliments of the Meguiars website, here's a quick introduction of what you need to do:
There are five basic steps in ensuring your car remains in show room condition. These can be defined as follows:
Washing – the process of removing above surface contaminants such as dust and mud.
Cleaning – the process of removing bonded contaminants such as tree sap, insect splatter and bird droppings.
Polishing – the process of removing fine scratches and swirls and producing a mirror smooth surface, thus enhancing the gloss and “depth” of the paint.
Protecting – preservation and sealing of the paint surface, resulting in a long lasting brilliant gloss appearance.
Maintaining – frequent removal of contaminants before they have a chance to bond to the paint surface.
I'm not familiar with all the products in your arsenal, but it sounds like you have most of the basics with some glaring ommisions.
Normal Garden hose - Good. Does it have a decent nozzle to allow you to spray the paintwork, wheels and arches etc?
Rinse bucket and grit gaurd - Good
wash bucket and grit gaurd - Good (You are obviously applying the "two bucket method")
Lambswool mitt (few months old) - Good
Microfibre mitt (few months old) - Good
Car plan - triple wax wash an wax shampoo - Hmm? You need a good car shampoo. Forget about the "wash n wax" part. It will probably suffice.
Turtle wax - wax it wet. - Ok. Keep it for the future
Turtle wax easy shine car wax (few years old, red bottle) - Can't comment
Turtel wax protective extra gloss - Can't comment
Mequirs speed detailer - Ok. Not the greatest Meguiars product. Keep for the future.
Turtle wax tree sap and insect remover - Good (You park under a tree)
Mequirs Quik clay sytem (unopened) - Very good.

You need this.
Turtle wax alloy wheel cleaner -

BAD. THROW AWAY. IT WILL RUIN YOUR ALLOYS!!!!
Poorboys world wheel sealant (unopened) - Very good.

You need this.
Halfords leather cleaner (almost finished) - Can't comment. There are better products
Halfords leather conditioner (almost finished) - Don't like "conditioners".
Turtle wax glass clean - Good.
halfords dashboard wipes - Can be useful.
Car plan silver T cut metallic paint restorer - Can't comment as I don't really know the product. Is it a polish?
You need a good wheel brush for cleaning those alloys.
You need a good drying cloth the dry the car after you have washed it. Not a chamois!. A microfibre waffle weave is best.
By pads do you mean the small round foam applicator pads? If so, you need them.
You need a whole lot of good quality microfibre polishing cloths to remove whatever products you apply. Not old t-shirts or rags.

By far the best trim detailer (IMHO of course) is Aerospace 303. You can use it for all plastic trim, interior, exterior, engine compartment, leather etc.
Right, so you need to do the following:
1. Wash the car really well and dry it
2. Clay the car - You have the kit
3. Polish the car - You seem to have polish
4. Wax or seal the car - You seem to have wax
5. Maintain the paint on an ongoing basis - You have some detailer but there is better.
May I reommend the following websites which will give you all the info you ever need
Detailing World - Very hardcore, you might get lost in there

Clean your car - Nice guys and a good online shop. I have used them many times. All the products you will need are on there.
I hope this helps. There are sooooo many products and everybody has there own opinion. At the end of the day it is not really about what brand you use, it is about how you apply the product. i.e. technique.