Well I took Jase's advice and started from scratch. I did less masking this time and used the data differently. I think this is a lot better than previous efforts and now looks a lot more like a nebulae than something I coloured in with crayons.
There is still some noise I cannot budge but overall I think it is getting there. I checked against a few notable astrophotographers and this seems close to the mark.
I know I have struggled with this image which I think is surprising for such a bright object, but the inclusion of the Ha data is really essential to how the image should look. I followed Rob Gendlers Tuts on this and have learnt another processing skill as a result.
If you like let me know what you think.
http://paulhaese.net/M8Lagoon.html