There's quite a collection of Brian fans here - in fact, a motley crew of ex-HB Society members, of whom I am one. No time for a longer list right now, but that Helios disc is a winner. For a single rec. I'd urge you most strongly to get the EMI twofer that includes, among other things, Brian's 7-9th Symphonies, all among his finest pieces; the 8th, though, is something else: one of my very favourite of all 20th century symphonies, utterly original, concise and powerful
As for the infamous Gothic - yes, it has choirs a plenty, of course, and the odd nice bit of solo soprano vocalise, but don't let that put you off. The first three movements are like a large-scale purely orchestral late Romantic symphony in themselves, fascinating in their mainly dark, brooding moods lit by odd rays of weird sunshine, the whole certain to grab the listener strongly by the throat. Indeed, you have the composer's license to stop listening at that point if you really can't stomach the vocal stuff to follow, where the mammoth forces really kick in.
Edit - Harry, I know it was a slip of the finger, but change the name in the thread title from Havergail to Havergal!