Nitrazepam has a pretty long half life, but consider that another benzo may not work for you. Midazolam, triazolam and brotizolam are very short lasting, I would advice against triazolam, it should be off the market. Loprazolam, temazepam, lormetazepam, etizolam, lorazepam are all short-intermediate, I would consider these ones since nitrazepam works for you and if you go with a very short half life alternative, you may wake up during the night or even have rebound insomnia. Temazepam is somewhat heavy too, lorazepam is milder but effective. Lormetazopam, loprazolam and etizolam all have a half life roughly 6-10 hours, which makes them ideal, but I don't know what's available in the UK.
I'd also recomend into looking non-benzodiazepine alternatives, just because the dependance on hypnotic benzos is unmatched. In many Asian countries flunitrazepam, temazepam, nimetazepam, midazolam and triazolam can be as controled as opioids, and that's because of the rate of addiction they had over there where they were prescribed a little too freely. So, just be open is what I'm asking. Some antihistamines are very effective.
