Ok well due to a crapload of RFS callouts (8 in the past few weeks) I only bit the bullet on repairing this a few days ago. I was going to ask a guy at my brigade who I suspect is a gun welder to take a shot at it - but I hate asking for assistance from folks...well unless it's online! So I did myself.

As mentioned my welding skills are not great and I only have a old entry level Arc welder. Anyway my work flow was kinda like this.

1. Dismantled the axle from the rest of the mower.
2. Drilled out the end of the sleeve, so that I could just barely get the broken end of the threaded axle end into it
3. Aligned the sleeve and axle so that the broken side matched the still connect other side
4. To support and 'centre' the axle within the sleeve I put a bunch of thin nails around the exterior of the axle in the sleeve - they were just the right size to support the axle and keep it dead centre.
5. Clamped this all down as best I could and welded the end of the axle to the sleeve - just lightly.
6. I then centred this before it cooled and then moved it into a vertical position and welded around the entry to the sleeve to the axle - did this quite heavily so there was a very solid bond between the two.
7. Then cleaned up the 1st weld at the end of the sleeve on a bench grinder and reinforced this weld.
8. Cleaned both welds up and applied come cold gal to them.

Put it back on the mower yesterday and seems both front wheels are very well aligned - I also reinforced the other unbroken side of the front axle while I had it off to ensure that it didn't break in the future. Again seems a terribly weak and poorly thought out design by Honda but I am pretty confident that the front axle is now a lot stronger than when it left the factory.

Am unsure if this has now also fixed why the rear left wheel was sagging when the spring was on it - I've still got it locked at a set height using a rigid piece of flexible steel - but might check this some other time - it's a PITA to align up properly IF its still not fixed and I've a bunch of stuff to sort out.

But much thanks to folks on the front axle repair - appreciate all the advice and assistance.