Benzodiazepines can take the edge off heroin withdrawal, they will calm you down and reduce discomfort significantly, but certainly they won't eliminate it completely. Definitely only to be used short-term as benzodiazepine addiction can be at least as bad to kick as opioid addiction if not worse in its extreme form. Apart from benzodiazepines gabapentin or pregabalin may be effective as sedatives to some extent, though I have no personal experience with them, seems like benzodiazepines are generally more effective, but like I wrote, and it can't be stressed enough, don't start taking them regularly, the dependence and withdrawal are hellish once you get tolerant, don't get hooked on their brilliant anxiolytic properties, it is so easy to do it.
If you can somehow get a hold of codeine or dihydrocodeine, these can diminish or even eliminate withdrawal depending on your tolerance, they're opioids but much weaker than heroin. If you take Subutex, then make sure not to take it sooner than at least 24 hours since your last hit as it can cause precipitated withdrawal, you really need to be in full withdrawal to take it. Obviously, if you take Subutex, then don't take weak opioids like codeine or dihydrocodeine, and also don't take heroin on top of it. Also, it is preferable to use buprenorphine only as a wean-off drug, a lot of people do report great benefits from buprenorphine maintenance, but generally the longer you stay on it, the harder it is to quit it too and quitting it is also quite different from quitting a regular opioid like heroin or morphine. I trust the doctor you're going to see will tell you all the info you need if he/she prescribes you buprenorphine, but you never know.