You can't be a "private" transporter for livestock... smallholders (who are usually the only ones with small numbers of sheep to transport) just do their own transport, an Ifor Williams P6 will take 6 sheep being towed by a family estate, off you go... but you will find that making a business of transporting those numbers of sheep is not worthwhile. You probably just have to do it yourself, especially if you already have a trailer/car to tow it.