Yes we have a lot of cacti and succulents around the house. It started with my wife buying just the one succulent as a curiosity, that split into several and even discarded leaves started growing roots to become new plants. It just built from there.
We now have Echevaria, Aeonium, Seedum, Haworthia, Sempervivum, Euphorbia, Aloe, and then on the spiny side I have a couple of good Ferocacti, Mammillaria, and some others I can't remember the names of.
All of our cacti were bought in garden centres or florists, some of the succulents too. Florists can have some good cacti (rather than the tiny novelty ones that are most common), they get them from specialist growers in the Netherlands.
Other succulents that we have were grown from baby leaves that dropped off a mother plant (including one tree Aeonium at Kew Gardens). Many enthusiasts are happy to trade leaves or cuttings.
There are however plenty of online sellers by the looks of it... maybe try this one?
http://cactusland.co.uk/main.php