We have Scleich toy animals. They're not the cheapest but they're lovley quality and very sturdy for little ones. My mum bought us most of them. She lives in rural Wales and apparently they are the farm animal toy of choice for farmers children!! They are stocked in a couple of independent toy shops near us but are quite widely available I think.
we also have the Scleich toys, and my ds nearly 7 still loves them so well worth the expence IMHO. He atill plays with them all the time and they are always the choosen toys to take on long car journeys and holidays.
Mothercare are doing tubs of about 8 quite large animals for £8. They are slightly soft plastic - like bath toys, rubber duck texture. They do safari animals or farm animals. Ds2 (20mo) really likes them (I have 2 hippos living in my handbag now).