Steve,
See page 9 of the March edition of Practical Caravan magazine which may help ease your concerns.
Briefly it states there had been an incorrect statement regarding AL-KO's view on motor movers in last month's magazine, it concludes with:
" When a mover is attached to an AL-KO chassis by drilling or welding component parts, this action would invalidate the warranty protection of the chassis. In practice, this situation does not arise as the manufacturers are aware of AL-KO's restrictions when their products are fitted"
Robert