Paraflu is the brand name ... and one normally sold by Alfa and Fiat. All you need to do it to make sure what you use meets the same spec. You can buy Paraflu from shop4parts (plus delivery) if you can't get to a dealer.
I've been using Halfords own brand concentrated coolant/antifreeze for a while now and it's fine. I mix mine 50/50 with distilled water.
The only issue you have is you really shouldn't mix the two types: one's blue, the other is red/pink.
Yeah I only recently found out about the whole green/red thing after having changed my thermostat. I'm pretty sure the one I topped up with, Texaco Havoline extra life, is OK with both types but got a bit paranoid so did a full flush and drain, fluch and drain before refilling with all red.
I think the difference is in the additive pack used and that additives used in green coolant can react with those in red to produce a nasty white jelly that clogs up the system as well as attacking seals and possible aluminium corrosion.