i reckon use hydro acid first, let it soak overnight, then rinse well, soak in petrol for an hour or 2 and then rinse extremely well.. then your coolant bottle should be as good as new, also its a good idea to flush your radiator and piping before you clean it, as i didnt and now i got brown stuff in it again!!!!!

i use the stuff i get from work that i use to strip tiled floors
its called ceramic tile plus.it does a dam good job im unsure if it can be brought retail

Ok after many searching i have decided to tackle the cleaning of my Coolant Bottle. This will best a test of what works best and what doesn't work at all. I looked at some of the most common responses and trialed the follow methods

Water & Stones, Shake For 15 minutes
Water & Salt/Sand Shake For 10-15 Minutes
Low Grade & Medium Grade Bleech
Degreaser & Shake then add water and try some more !
Pool Hydrochloric Acid, let sit on both sides (Available At Clark Rubber or Any Good Pool Store)

First, how to take off your coolant bottle
1)Wait for the car to cool so you dont burn yourself (common sense)
2) Disconnect all 3 Hoses (One Under Bottle, Two to the left)
3) Undo all Three Bolts (two on the bottom, one on the top)
4) Remove Bottle

Then mask of all holes except for the top one

Results
Acid: First i used the hydrochloric acid and this stuff is dangerous but its only pool grade so it was ok, after sitting it on top and bottom (with cap on and all holes masked) it had done alot of work to the bottle, this stuff worked great but should not be touched with your hands or make eye contact.

Stones & Water: worked ok when i tipped all the water out some dirt surely was moved but the fun did not end as getting the rocks out is the hard part.

Salt & Water: Doesn't Work, made no difference

Degreaser: It was fun to shake but did not help anything

House Hold Bleech: Using about half the Coolant Bottle with bleech (all i had) and mixing with water followed by a good shake did make a difference, it helped remove alot of dirt but was hard to get rid of once i was done.

After all the time spent i did like the result i can see the Coolant Level now without taking the cap and i should be able to get a picture up soon (i did take shots of all of this in action, but my memory car $#!t its self. Also there are many methods out there i just used what i could.

Conclusion:
Best Method: The hydrochloric method was the most effective but the bad thing was that it burns are is a health hazard.

Most user Friendly: The Bleech or Stones and Water would have been what i would have used if i could not get my hands on any hydrochloric acid.

how much is a new bottle btw? (to those who went and bought one)