Personally i'd stump up the £120 from toyota. It isn't something you'll want to have to do again and a toyota one will last for the remainder of the life of the car.
I had one on my old MR2, wasn't bad really did the job. Bleeding is your main issue you will get a fair amount of coolant leak while you're bleeding but if you persevere they do a good job and are an upgrade from the original.