Yeah, too bad all cathinones except fresh Khat itself are now illegal in most of Europe. I had a similar experience to the OP's when coming down from a high dose of 4-MMC: I had no benzos, no weed, hadn't eaten for days, so booze was out of the question. My stash at the time was all stimulants, nitrous, which was fun on meph comedowns, but only took the edge off for about 5 minutes per balloon, salvia...and some Kanna, which I took for its sedating properties: forgetting it's a virtual SSRI. Sweats, hot flushes, nausea, headache - it was kind of like a sudden few hours of intense dope withdrawal, combined with a psychotic sense of mental 'overheating.' Pretty much turned me off of 4-MMC, as did witnessing people take to it with the fanaticism of newbie crackheads. A lot of people over here got into serious trouble before the ban, using daily at work, et cetera: it was deceptive stuff, superficially similar to MDXX, but with that methy edge of easy addiction and psychosis. Of course, the ban just means it's now cut to shit with God-knows what.
BK-MDMA was sweet, though - wonderful for sex, almost worth the grinding, lengthy comedown, and a very pleasant social lubricant, especially if there was plenty of weed or a benzo or two to end the night on. The rebound insomnia and anxiety, otherwise, made it seem a long fall for a short slide, on its own.