Cheers for the comments chaps. That's why I come on here to get some top advice. You were far too nice on my first fly!
I've just had a look again at the GB article again and his "original CB" and I agree the rib is too wide, and it needs more seal fur, but I also noticed that I need a lot more hackle!

That's mostly to do with the cheap capes I have currently in these colours - though I felt my credit card twitch last night when I saw Saracen's capes

The tail in GB's pattern was listed as something like "short and stumpy", and if you don't have any dyed tippets, then he suggests you "scribble on them with a red pen like a 3 year old"
ok I made the last bit up