Where to head for northern winter
 

So I'm currently in the early stages of planning a trip from Australia to Europe via India, Pakistan, get on the Pamir Highway etc
I really want to go through the mountains in the north of this area, which as I understand it is generally only passable in late summer (July/August), which would then have me getting to Europe as the weather is turning. I'd love to head north into Russia but probably not ideal this time of year, so open to suggestions, considering that I don't really have a final destination set or anything like that.

Cheers

Have you considered do it the other way around? Ship your bike to Europe in the spring and ride back to Oz, this might work better with the weather and your itinerary.

The Iberian peninsula (Spain/Portugal) is generally pleasant and rideable even in winter, at least the flat bits.

True - although I'm a little limited with the 90 days limit in the schengen zone per 180 days, would prefer to spend some time in northern europe when I would actually be able to enjoy it. May be better off looking to leave the bike somewhere and fly home to try pick up some work or some such thing. Don't particularly like the sound of that though...

You could spend some time in the UK - it is outside the Schengen zone. If you are Australian then you could possibly work in the UK.

As Mark has said going from Europe to Australia may work better and allow you to travel in reasonable weather the whole trip.