Morphine is much more sedating, and is similar to heroin without as intense of a rush and euphoria, as heroin acts a prodrug to morphine that crosses the BBB much quicker. Morphine is too powerful and too addictive for your purpose. For reasons I don't yet understand, natural opioids like morphine and codeine are more addictive and induce more cravings than semi-synthetic ones like hydrocodone or DHC.
I would start off at 5mg hydrocodone, but since you're in the UK, 30mg of codeine (equivalent to 5mg Vicodin). Just make sure to do a CWE properly if you are buying those 8mg co-codamols OTC.
Stick to kratom, codeine, hydrocodone, DHC, and tramadol with the oral ROA
only. Sticking with weaker opioids and oral administration will greatly cut down on the chances of addiction and will make walking away from an addiction worlds easier than craving an intense high from snorted or plugged opiates. Don't insufflate or take a huge dose even once, because then you will set the bar higher and you will never be satisfied with a weaker oral ROA.
From another thread on Bluelight:
You have to police your own tolerance. If you find it is increasing too much, then you have to cut back on your use. Also, don't take higher doses than you need, and if your dose no longer gets you high, then instead of increasing the dose, take a break instead.
I agree, this is the best advice you can give to an opioid user. Instead of chasing the high by raising your dose and never catching that dragon that you played with during the honeymoon period, take a little break, or just chill on a maintenance dosage, which is 25% your usual dose just to avoid sickness, then you can play with the dragon again in a couple of weeks.
You can either spend your whole opioid career chasing that dragon every day and never catching it, and end up with unsatisfying morphine blue balls, or you can play with the dragon when the time is right and let it fly away when it wants.