I'm looking forward to Dawnguard but I've heard from my friend that a lot of it is related to Dragons and the main quest in general. This could be sometning of a problem because I don't like to play the main quest.
I've never really liked to play as the hero that saves the world, I could kind of get over it with Oblivion, you didn't need to be a chosen one to fight back the Daedra. Similarly in Morrowind there was always doubt over whether you were born as an incarnation of Nerevar or whether through your acts as an extraordinary individual you became it.
With Skyrim you're made out to be the Dragonborn, the only guy destined to save the world and I find it a bit lame really. As a result none of my characters have ever made it past meeting the Greybeards for the first time. None of my existing characters have even been to Dragonsreach.

If thats a little too long for you to read, just know that I find the main quest dull and uncompelling and I'd rather not play it. Do I need to have a degree of Main Quest progress to play Dawnguard?

(I decided to post this here because there will inevitably be spoilers if it turns out I do need MQ progress)

nope.
the only thing you have to do that is main quest related is to go to blackreach to get the elder scroll and thats it.

Jolly good

That isn't even really part of the main quest anyway
It technically is part of a Daedric quest

You need the elder scroll from the main quest, but getting it anytime before the quest you need it, even if not doing the main quest at all, will not affect anything. As Hudomonkeys said, it's not really part of the main quest anyways.
You will miss out on a really cool fight against two dragons that can dive under ice, and possibly get stuck with a misc. quest to summon a dragon (exiting dialogue may prevent it from popping up, but not too sure) in your quest log. But no, you do not need to do the main quest at all.