I'd go with promethazine...sold OTC in the UK for some reason....script only almost everywhere else.
Brand name is Phenergan...it has sedating/anti-emetic properties & is excellent as a potentiator for opiates/benzo's.
if you are UK based, you have to ask for it, they keep em in the back. They will ask what you want em for, say travel sickness.
*edit* they come in packs of 56 25mg's, & will cost you about £5. Dont be fobbed of with the 10mg packs...they cost almost the same as the 25mg's
Fuck I hate suspicious chemists, some of em think they know as much as doctors...which isn't saying much lol