I'll repeat my tip on dealing with Kadee (and similar) springs.

Get a foot of fine sewing thread and run it all the way through the spring. Set the spring fully in place, ten remove the thread.

Separating springs usually requires a hobby knife and the Kadee spring pick. 

Gentlemen,

The worlds most annoying piece of brass has been removed from the boiler!

I came back to it this evening with a better frame of mind and the right tools, and after some careful heat application and some extra solder, it came out after 4 months. 
 

As you can see in the images, the fake boiler backhead plate was removed for better access.

The part did get rather chewed up from various pliers though. 
 

So now I intend to clean up the backhead, and re install the stock whistle after going through the threads with the correct BA tap (I have a full set now). 
 

Douglas

Just now, simontaylor484 said:

Thanks for that these have already been turned once there is still a bit of life in the blades but not much

Reminds me of an interesting conversation I had on a train once with a complete stranger.  His firm had a contract to replace the paving and steps outside St Paul's.  They wanted to save money by turning the steps over but found out that the Victorians had already beaten them to it.  I guess that it was worth trying though.