Warm roof or cavity wall insulation ?

Thanks alot for posting your videos on you tube, i found this 1 http://www.youtube.com/watch?v=wyNviteSOzY
very helpful.
I currently have a flat roof extention for my bathroom and kitchen, this is how i bought the house btw, but it has no insulation and it
leaks also..
My walls are cavity on the extension but they are not insulated, my question is, would i be better fixing the roof with a warm roof or
filling the walls with insulation??
Can you tell me if i can get away with fixing 1 or if i have to do both?

I really appreciate your time steve, im dad of 3 and everyone complains how cold the house is and im sick of huge gas bills i cant afford.

Any advice would be greatly appreciated..

Best Regards
ben..

ps im thinking of doing a warm roof myself but im not 100% sure how the due point works, sounds tricky and not something u want to get wrong

Hi ben if I had to chose between warm roof or cavity wall insulation it would be warm roof first because at the moment the roof is the real week point.