You can buy online from Pet Planet:
http://www.petplanet.co.uk/product_group.asp?dept_id=45&pg_id=442

I buy the big 15Kg bag for £36 but it lasts for ages - depending on the
number of cats using the litter, you only need to do a full change every
14~21 days.  My last bag lasted me three months.  The trick is to take the
lumps out daily.  I use a litter tray with a hood and which has a carrying
handle, so it makes it easier to carry the tray to the bathroom and then
flush the contents down the loo.

I buy stuff from Pet Planet quite often - cheaper than going to Pets at Home
or Petsmart, and they are very reliable.

It's expensive..! We've just started using it at the Cats Protection
shelter where I volunteer and I got told off for throwing too much away..!
Not sure where you can buy it though, obviously we get it in bulk. It's
good stuff though, I must admit.

Ivor

I used Swheat,too...but couldnt find it all the time in stores. I cannot
tolerate dusty cat litter...My allergies will not permit it...along with the
ammonia that comes through from urine..we have 7 cats..so I use anything
that has maximum odor control.

No clumping no smell no dust the urine seems
to soak in the bottom crystals and stays there.
I keep my boxes in the basement clean them weekly
the dust was awful before using the crystals and the
cats don't smell like a litter box. The clay clumps
used to stick to my long haired cat and she was
leaving dropings and scared when they stuck to her.
I used to also find litter on my floors from it sticking
to their feet. The crystals cost about $14.00 a bag
and last a month, I buy a bag every month.
I hope this was helpful.

Jan