Hi paul.
i had my freezing problem, i think it was pugwash who wrote this:
WhenWhat you really need to do is drop the fluid fmro the engine and replace with proper toyota red stuff- which iirc protects down to about -34 in it pre-mixed form- we're never going to get that cold in the UK, so pre-mixed should do you fine. You can buy concentrated but ideally you really should use de-ionised condensed water to mix.
Thanks karl