Ideally, run it to temp, cool it down then drain/refill.  All you need is to drain/refill, run it for, say, 5 minutes to circulate the water then drain etc several times.  Yes, it will take a few days this way.

Alternate if you feel confident is to place a hose in the water expansion tank and balance the amount of water going in with the amount draining out the radiator drain.  Start the engine and keep a GOOD eye on whats happening, water level wise.  Do not let it fall below minimum.  Leave it running (still watching   ) until it all runs clear.

right, so im back to VX on Monday then to buy ANOTHER 5 LITRES of the red stuff?
and i wasted £16 on Forte coolant flushing stuff that just p****d out all over the place

im VERY fedup

so, Monday....first of all, it`s empty the radiator again from cold? drain everything out straight away
put the radiator plug back in, fill up with water, start engine and leave running for how long exactly?
then let engine cool down, how long to cool down so i dont scold myself with the pressure from the header tank?
then empty again.... refill with water, plug back in, and do this how many times?
how do i know when the water is gonna be clear so that when i refill with the red stuff it actually stays red???

im stupid!

OK, lets try a step at a time....  

From engine cold.....
Unscrew coolant filler cap and insert hose.  Water not running yet.
Put car heater on full hot and have heater fan running.
Unscrew drain tap.  Remember it does not need to be fully removed, only unscrew far enough so that you get a reasonable stream, leaving the red plastic bit still on the radiator.
Start hosepipe running so that input from hose equals output from drain.  You know its correct if the water level stays about the same in the header tank.
Start the engine.
Remember you are adding cold water to a cold engine that does not really get the chance to warm up properly as you are always substituting cold water in for the hot draining out.
Leave it running for about 20 minutes (should be enough) but ensure that it does not overheat by regularly checking the temp guage.  It might need longer.  When the water runs as clear as a clear thing, all should be good.
Switch off engine, switch off hose, leave drain tap running until it stops.
Close drain tap.
Let engine cool.
Add 5.5 litres neat red coolant.  Top up with cold water.
Still with heater on hot, with heater fan on and expansion cap OFF, start engine.  Regularly squeeze the large radiator hose (2" diam approx) beside battery to expell air into header tank.  Keep an eye on lthe water level topping up with cold until engine reaches normal operating temperature.  Replace coolant cap, take it for a short drive to ensure alls OK, then park up at home and leave it overnight.
In the morning check the level again and top it up.  It will have dropped slightly overnight.
Adjust the heater etc and drive as normal with a large smile on your coupon, confident in a job well done......

We posted at the same time. Leaving water only in the system will be fine for a day or two.  Just don't forget to add the coolant and don't rag the car too hard in the meantime.  The red coolant is antifreeze but also a corrosion inhibitor and water wetter/temp transfer agent as well.

reckon i should drain and refill it 3-4 times per day for 1 week?

and making sure i run the engine between each flush?

so really i need to go and spend £25 on 2 big 5 litre tubs of the red stuff
as i will need to add it each night (incase) it gets cold?

this is all becoming more expensive than i imagined

i suppose your right

i may get 20 litres aswell

i wonder IF we can have a competition to see who has to have the most flushes?

bet i win!

my car has had regular oil changes every 5000 miles, filters, etc etc
and the coolant has just been drained and refilled, but as far as im aware NEVER flushed like it should have been

i just popped out a minute ago, ran heater at HOT for 25 minutes
will make sure i do this everytime im in the car, damm..its gonna get boiling!
this is the best way to clean the crap out i take it?

i dont suppose ANYONE is popping to Vauxhall near me?
would be good to get 20 litres and NOT pay £45 !!