URGENT!! Withering indoor clematis

Ok, so I bought a clematis about 3 weeks ago or more and it is living inside till it is strong enough to go out in our british weather.
However it has been wilting and looking dry on the leaves ever since.
I tried re-planting into a bigger pot with fresh compost and that hasn't worked.

I read this;
http://www.howellsonclematis.co.uk/Pages/Gnews14.html

Is it this that is causing it? Or this:

I don't know if its what the problem is?:
http://www.rhs.org.uk/advice/profile...matis_wilt.asp

Would value any advice. Please can somebody help urgently- as I don't want it to die!!!!!