... where I can buy these on line (these ones, in case there are others http://www.kongcompany.com/worlds_best.html).  I want to get some medium ones as Roxy adored them and none of the pet shops in my area sell them (although they sell Kongs).

All help gratefully received.  :)

I've never seen the kong biscuits but I bought some foamy mousse stuff (liver flavour) that is made by the Kong people and cost approx £5.  I read the packaging wrong and although it said to squirt into the Kong for a few seconds (which I did), I thought it said approx 40 servings of approx a tablespoon per serving which I thought was fairly economical.  DOH! When mine ran out after 3 servings I was raging until it was pointed out to me that tsp is teaspoon not tablespoon and no wonder my dog was luvin me for feeding her the equivalent of approx 10 pots of chocolate mousse at a time and her tea!!

Thanks Cheeky Chow.  Does the mousse stuff set hard?

We got three free biscuits with the Kong when I bought it and she really liked them.  I think it made the Kong special in her eyes as it was treats she'd never had before.  Each time we brought the Kong out for her, her little face lit up (as much as a white dog's face can :D ) and I'd really like to try and get them for her.

We too have the mousse and it does not set hard but our cav loves it.  I have been to our local pet store today and asked out of interest about the kong biscuits because nothing we have seems to stay in.  The girl there said to use James Wellbeloved Minijacks treats.  They work very well.  Flynn has been trying to get them out for ages. 

As Flynn is a puppy and a small dog we have the small puppy kongs but these treats come in 3 sizes Crackerjacks (big) Crackersnacks (medium) and Minijacks (small).  They come in four flavours too. Duck, fish, lamb and turkey and are Hypo-allergenic. 

They might be worth a go.

If you find the Kong biscuits please let me know.