For a flush, I use whatever I find. Holts used to be the best known brand but you might find Car Plan or something. In some cars you can easily take out the expansion bottle and scrub it clean inside and out at the kitchen sink. Often a lot of the dirty appearance is staining and sediment inside the bottle. If you can't remove it, wash it out with a hosepipe before you add your chemicals.
As for antifreeze, the pink is a more modern specification, last longer, and costs more. Newer cars will demand it in the handbook.
IMO if they are made to the specification, it doesn't matter what brand you buy. Approaching or just after winter you often see good deals.
I recently bought mine on a 3-for-2 offer at Halfords, then saw
Wickes had it at a much lower price. I would have bought Tesco own-brand if it had been cheaper.
Work out how much you need, if you have several cars and you don't know when it was last done they need draining and then you can probably use a 5-litre pack which (subject to special offers) will be better value than 1-litre bottles. I usually mix mine to the "extreme" winter concentration. The readymix coolant is usually worse value than the antifreeze concentrate. Look at all the hoses and replace any ropy ones before you change the coolant.
