Hello Ken et al.
So I finally managed to get into it. As suspected it was the cache - i turned off edwiser to no effect, and got a constant redirect. Essentially i had to rename all of the /cache/ subdirectories until it let me in. Turns out that the cache in question was /cache/stores/file/ - renamed that to _OLD and it let me in without redirecting.
Then purged all caches and we are cool.
Well, cool....except that I have no CSS. Apparently there is something odd about NGINX which isn't feeding css or js files properly.
If anyone has any info on that I'd be grateful!
But thanks for all your help guys. The site, although currently in text format only, it at least working!
Hugh.