Ketamine isn't a controlled drug in the UK (yet!), so it's not that uncommon, but I find it tends to turn up in cycles (something to do with the way diverted ketamine turns up in a place), probably to do with how it's not an offence under the Misuse of Drugs Act to import it (again, parliament seems to be getting rather interested in the degree of ketamine use with an eye on legislation).
If the market was profitable enough, you'd get clandestinely manufactured ketamine turning up (bit like LSD in the 60's before any serious legislation occurred) as it's not that difficult a synthesis, but at the moment all the people involved in such things will be manufacturing PCP due to it's increased potency - about 10x that of ketamine - and established acceptance/market meaning there's more profit in it (today's PCP manufacturers aren't quite as idealistic about it being a 'sacrement').
I though that just about everybody I know who liked opiates would like ketamine, but at least one friend who had a friendly relationship with opiates said that the didn't like it due to its air of confusion, both physically and mentally. I suppose you do get that detachment from the reality of everyday mechanics & stresses of life, it's just that you don't seem to be able to identify the reality that you're escaping from! Whereas heroin is a totally effortless experience requiring almost no input from you, ketamine tends to have moments of really exercising the brain where you try to fit everything around you to your 'normal' model of reality. It takes a while of desparate floundering, mentally screaming,"What the fuck is going on here?" until your brain gives up and the thought that it's ketamine can now get to the shards left of your conciousness that are left. It's accompianied by a low sort of hum in those moments, so it's not quite the 'couldn't give a bugger' relaxed state of heroin/opiates.
It's a very relaxing experience if you just ignore most of the chaos that comes with a fairly rapid shutdown of sensory input. It is something you become accustomed to and even look forward to after a while, as it means that you're on your way and your ego is about to fragment like a cartoon character beaks when they're shown as cold and hit. If you insist on trying to make sense out of it you can get quite a shock as nothing confirms to your usual internal model, no matter how hard you try. If you're a 'a place for everything & everything in its place' sort of person, the ketamine experience can get to be a real pain in the arse