Cave diving to -312m

Yes, that's it! The question mark was supposed to indicate the need for imagination. Over to you . . .

OK, time for a more substantive hint. The clue is perhaps a bit indirect - in fact if there were such a place as "Fringe Pot" the phrase you are looking for might serve as a clue to it. Oh, and an anagram is involved . . .

It's not easy to come up with a hint without giving this away. For now, I'll just suggest that the letter count should narrow down the options.

I think the OMG was a bit of a red herring. Then Spock is an original Star Trek reference (although strictly he was only half Vulcan), and his top backwards gives the second word. Meanwhile, try this one: Fringe Pot? (6, 6, 3)

I suppose the obvious answer would be Vulcan Pot.

That's it - over to you . . .

Market cavities in fish parts? (4, 4, 5)

I'll go with a bit of a guess, maybe Valentine Hole?

That's the one.

Women's magazine encloses old conductance unit (3, 4).

That sounds like Groundsheet Junction.

Just wondering - is Vol. 1 available anywhere?

That's the one!

Pet pony disturbed outside Belgian city (9, 3)