Hi pj
Not a problem moving your axle they are usually just U-bolted into position. Firstly mark with a marker pen where your existing axle postition is on both sides of the frame. You can then move the axle in the comfort of knowing your starting position. This will allow you to relocate it if necessary and also aid in keeping everything in allingnment, assuming its set up squarely now that is. Try a little at a time say 50-70mm as a little can make a big difference in the balance of things.
Martin