I think i've reached the end of the road with this search. My main 12 word phrase does not seem  to work in either mycelium, electrum, bitaddress.org. Not tried Multibit; but I'm sure it won't work there either. I'm gutted; and also annoyed because I know it should work.

The thing I found strange was that my other 12 word phrase that worked for Electrum and revealed historical transactions also worked in  Mycelium.
 
I'm going to park this problem for a while till i get fresh ideas; but thank you to everyone that helped esp. nc50lc and ETFbitcoin.
Thank you.