I encourage you to stop IVing, although I am wondering if you added citric acid to the water to allow the heroin to dissolve. The heroin base you get in the UK doesn't dissolve in a neutral or basic solution, so you need to add something like citric acid to alter the pH in order for the heroin to dissolve properly.
I'm wondering if anybody actually enjoys the rush from IVing, or the experience as a whole, if they aren't already strung out. I feel like the rush is just a reminder of the instant gratification to come, therefore the feeling isn't what is enjoyed as much as the association with getting high. I would say that most people that IV heroin are already strung out on another opiate, or have a tolerance to sniffing or smoking heroin, so I'm wondering if somebody with no real tolerance to opiates enjoys the IV rush before the association is made in their brain.