On a similar hunt myself
Me too...Or I was.
When I converted the loft into a Computer room / Music Studio / Porn stash, I just floored it and that was that.
It only took me one winter and one summer to realise that its simply not possible to cope in there...
Winter time was brilliant for overclocking, but in the summer I would be naked all the time I was up there, and thats not a pretty picture I can tell you!
Anyway, I re-done the lot, pulled up the entire flooring, and removed all previous bits of stuff, put the stuff down nice and thick, put the floorboards back, and also did the roof too, this time round however, I also used the foam filler stuff to fill in the cracks where wind was getting through - there were loads and its quite shocking really.
Now, my loft is comfortable all year round.
I think that a big help, was actually putting down a carpet in there too. Not fitted, a rough cut that does not quite reach the sides is all thats up there, cos its an old one from the living room, but its enough for a room thats only for me.