Thanks for your help wp, I dont think this time I'm helpable.
I have a dht11 working well, after I'd tweaked the timings, the '11 seems to be ok unlike the '22.
I cannot get the dht22 to work, I've tried the shorter request pulse and various pullups including none, and altered the timings.
I looked up on the net to see if others have used the dht22, and when I did that I found that loads have had trouble, saying things like the data sheet is a lie and timings are off by near 100%, making me think this sensor is pants (or should I say unuseable without an accurate datasheet), no wonder the better suppliers dont sell them.
I see there are files available for the arduino that do work.
I think these can go in the bin and I'll go get a dallas temp sensor and a discrete humidity sensor and go through the salt bath callibration procedure, I dont have time to mess about code breaking to get the sensor to work.