HURRAY!!! I am in.
I was just about to write that I have created 3 whole new DW sites and have looked at all that documentation and was going through it all again to point out particular areas of uncertainty when I noticed the PORT NUMBERS were different. I had been very reluctant to fiddle with things like that as I had had MAMP all running before and it was giving me its 'all well' message but I gave it a shot and hey presto everything works.
Thanks very much indeed.
PS Though it seems my problem was in fact stated in the available help I cant help pointing out that the instructions are very confusing! It would be a lot better if it was all in one step by step document ... but what the heck I am glad I am in at last.