@Daz_Falco You replied to a thread with the latest post being from 2006. Safe to say in those many years, the sites were shut down.
For port information, you can use sites like : https://portforward.com/half-life/ - https://support.steampowered.com/kb_article.php?ref=6470-EIFV-5481
Checked out some gameplay videos online regarding the update, and it looks pretty sweet. Almost keen to actually grab the game myself eventually. But I'd say the game will take up a lot of your time to actually get somewhere, ain't it.
You linked your forum account with steam, not half-life.
Though, the current half-life verification system is broken so you couldn't do it either way for the time being. Hopefully, will be resolved soon.
I tried multiple times a few weeks ago and the OK button magically appeared for me. The only thing that I can think of is that somehow when you run the installer it's not properly finding your HL directory accordingly which you already knew. Mind "connecting" your steam account and doing a HL...