OP I'll try and answer your factual questions.
Surprisingly it isn't illegal to import drugs which are prescription only in the UK, as long as they're not controlled drugs (class A, B or C). The government is currently analysing the results of a public consultation on whether to reclassify Pregabalin and gabapentin as class C drugs. All the benzodiazepines, including diazepam, are class C already.
There are several websites which will sell you the drugs if you can provide a prescription.
There are some websites which will sell you the drugs following an online consultation with one of their own doctors
There are a few websites which will sell you the real thing without any prescription (these are based abroad). However these sites won't supply controlled drugs to the UK.
There are MANY websites that will sell you something with the same name as the drug you want, but God knows what's in them. Many of the tablets supplied turn out to be not what they say they are, but something even more dangerous.
It depends which site your DH is using. If you know and want to pm me, I'll give you a heads up.
It is only legal to obtain these drugs for the use of self or very close family, but that assumes that they are used responsibly. If anything happened to DH and the inquest found that you had ordered the drugs, you couldn't prove completely (even though he pays you back) that you weren't complicit in his death.