Unless the UK is very different, it shouldn't be entrapment to let them try to buy it. IANAL, but in the US, entrapment as a defense requires "the defendant's lack of predisposition to engage in the criminal conduct".
Which, by the way, is absolute bullcrap. A classic example is an undercover telling people at a methadone clinic that they've been cut off because of a paperwork snafus and begging people to share their legally prescribed methadone so they don't go into withdrawal. Because anyone at a clinic treating drug use has a predisposition to use illegal drugs, it can't be entrapment.
Your sentence is confusing because of the unclear use of "they". It sounds like in this case an undercover cop would come to someone asking for their controlled drugs and you're arguing that it should be entrapment.
If a citizen approaches an undercover cop and offers to sell their controlled substances that isn't entrapment.
If an undercover cop approaches someone and asks to purchase their controlled substances that should be entrapment.
Police shouldn't be able to ask you if you want to commit a crime, it muddies the water of intent. If the police hadn't initiated the crime by asking, would the citizen still have still done the illegal thing?
Standing up a honeypot is different. If someone is actively searching for a good or service and initiates contact with the honeypot, intent is clear.
For me, part of this is "give an inch they take a mile." Letting police ask you to commit a crime is an inch. Then the police get convincing with lines like "my babies are at home, we cant make rent and I cant afford formula. I'm trying to get clean anyways, can I sell you my 8ball for some cash? No no, I can't accept charity. No no, I don't have anything else to sell." Perhaps the citizen doesn't do drugs, has no intention of doing drugs, and is foolish enough to think they can give this person cash and toss the drugs in the nearest trash can once out of sight. Instead they're getting handcuffed because a police officer pulled at their heartstrings and tricked them into "buying drugs."
So, any conviction that starts off with "that guy over there is my dealer", then the cop goes over and asks to buy drugs, the dealer flashes open his coat, those should be thrown out for entrapment?
To put it politely, No thanks. I'd prefer it to keep working as it does.
The undercover cop is asking people for controlled prescription drugs. The cop claims they have a medical need and a prescription. The cop says the only reason they can't get the meds legally is one of the standard system errors that delay getting drugs in this country.
Let's call the person giving the drugs Sally. If Sally has a previous conviction for drug-related crimes this isn't entrapment. If Sally has no criminal record it is entrapment and she walks free. I think she should walk free regardless, i.e. it's always entrapment.
It's relatively readable, it's probably enough to note that a "stay" means that a trial will not proceed (at all).
A quote from that section:
"Police conduct which brings about state-created crime is unacceptable and improper, and to prosecute in such circumstances would be an affront to the public conscience. However, if the accused already had the intent to commit a crime of the same or a similar kind, and the police did no more than give him the opportunity to fulfil his existing intent, that is unobjectionable."
