Right. I now have six nozzles with 2 mm holes

For those of you who are reading my "LPG versus JD" saga I did this the following way.
First things don't bother with a soldering iron. You need to get the nozzles hot. I found a plumbers blow lamp far more effective.
So take nozzle O ring off and gently hold with a pair of mole grips
Heat the nozzle. It doesn't need to be red hot. I did a mild count to 30.
Remove the flame. I found it easier this way.
Then just keep feeding the solder in to the nozzle. The mole grips do a good job of retaining the heat.
Wait for it to cool (this is important. Trust me I managed to pop the solder out on the first one I did)
Then once cool drill to size.
Simples.
If you balls it up just re-solder. Pays to have a steady hand. First one I did the solder flowed over the threads. I just heated it up again and wiped the threads round to remove it.
Tomorrow I'm going to pick the fannymould up from Kev. This really is the last bit of the puzzle. I'll fit the Manifold nozzles up and then I'll crack on the Weekend. Once again I owe it all to the Guru's on here. I'd never of thought of doing that.

Anybody who thinks this is a bodge. Get over it. I won't be buying anymore jets. I will now just take them out in 0.1 mm steps till I hit the sweet spot. If that turns out to be 2.5 mm I will open my tool chest draw, line it with broken glass covered in chopped chillies then repeatedly slam my genitals in the draw.