Many thanks, Humayun.
And this is M17.. Thats a wrap for me tonight I think....
The final cause of the squares around stars after a very stringent investigation... The way in which I was converting the 32bit TIFF to 16bit for processing...
I still had photoshop set to "Localised Adaption" from when I was last playing with HDR terrestrial imaging.. I changed it from localised adaption to equalise histogram and the squares dissapear, as did the odd looking fuzzy appearance of the images...
Seems first light went much better than I'd originally thought!! (WOOOHOOO!!!)
Cheers all
Alex.