ChoicesUK are selling "Purr Pals" for the Nintendo DS for £5.99 (inc Del.)
You can get cashback through the usual sites (e.g. 5% Quidco, making it £5.69)
The next best prices seems to be £12.89 from dvd.co.uk.
Calling all kitten lovers, Purr Pals is the game for you! Now you can choose your favourite breed of virtual kitten to adopt, raise, train and care for on your Nintendo DS. You can completely customize your kitten and their environment by using cute toys and accessories that will enhance your kitten's unique ersonality. It will respond to your voice as well as the environment you provide. Your adorable kitten will create its own distinctive personality that you can influence with love, care and affection! Adopt your favourite breed (40 different breeds) each with unique kitten personalities Use proper care and training to meet your kitten's needs and desires Modify your kitten behavioural traits Customize your kitten with limitless choices Utilize voice commands that your kitten will react to Train your kitten with toys and food Interact with your kitten within the environment Multiplayer mode allows you to interact with friend's kittens Play fun mini-games with your kitten