It's not often I put my hand up in public and admit to being a Plank with a capitol P. If you use the 1.2 software to try and update your Spirit to 1.3 you won't find the file. So, me being old and from the old days I thought i'd change the new file suffix to .bin.
Excellent, it loads the file and then I got a loverly little red paperweight. So the morale of this story is use 1.3 software to load the 1.3 update file.
It took Tomas all of three minutes to sort me out. Excellent service, many thanks Tomas!