^ It isn't an especially powerful hypnotic, so if you happen to be unable to fall asleep after even a low-moderate dose of Stilnox during an unpleasant psychedelic experience, you might find that shit gets a whole lot more topsy-turvy (check out the threads on recreational Stilnox use if you've never remained awake under the influence of this strange drug).
Also, the reason you paid much more for your Stilnox is because it isn't PBS subsidised, so you pay the full cost of the medicine (a 'private' prescription), as opposed to most common benzodiazepines, which are PBS listed and are thus cheaper.
As for a good weapon to have on hand for when psychedelic journeys go awry, you might be interested in visiting the doctor for a less conspicuous drug than those of the benzo family, and one that will possibly prove quite useful - since many adverse psychedelic reactions are essentially temporary psychoses, emergency wards in hospitals often administer a combination of an antipsychotic + a sedative. A common family of antipsychotics is known as the 'phenothiazines', and amongst these drugs there is the well-known promethazine (Phenergan trade name - S3 medicine therefore available without prescription), which is used mainly for its histamine antagonist properties, and also prochlorperazine (Stemetil/Stemzine trade name), which is an antiemetic (antinausea) and achieves this mainly by acting as a central dopamine antagonist.
So, two good drugs to have on hand in the event of a bad trip might be promethazine, which will make you pretty drowsy at even normal doses but isn't necessarily a potent antipsychotic, and if you visit your doctor and explain that you have (for whatever reason) recently been feeling nauseous, you might even request Stemetil tablets (they've worked well in the past ey!), which contain 5mg of prochlorperazine each - when administered as an antipsychotic in acute and chronic psychoses, the adult dosage range is more in the avenue of 75-100mg, at which you can also expect significant drowsiness (and other side effects; always research further).
NOTE:
--Having listed two separate and potentially useful phenothiazine drugs does NOT mean that I am suggesting the two of them should be administered together; they shouldn't.
--I have no personal experience with the use of these drugs in acute psychoses arising from psychedelic experiences, and please take my advice with a grain of salt - the above is merely information, not recommendation. But if you research the topic yourself, you will hopefully find information that confirms and expands on my advice.