It's important that the beam is perpendicular to the plate.  Otherwise, you could have cutting issues (like tapered edge, or cut issues in 1 or 2 directions).
If the beam alignment is good with the head up and down, then I would think that your nozzle alignment issue might be related to a mechanical problem with the head up/down movement.
If you don't have cutting issues, and you don't mind having to align the nozzle at the plate height, and you don't have to cut "non-flat" materials, then I guess you could leave it like that.  In normal condition though, you should be able to align the nozzle at any height and not worry about head position.
If you are using a small nozzle (0.8mm for example), and the nozzle alignment moves by 0.3mm, it could be too much and cause cutting issues.  If you're cutting with bigger nozzles (2mm for example), 0.3mm movement will probably not affect anything.

For the mirror alignment, with some training, you should be able to do it yourself.  It's really not that hard.  Sometimes it just requires some patience.

Thanks, well i think i will try to get someone to show how its done then. Got issues with cutting if i got long pices and the tension in the sheetmetal pulls it up.

If the head has been whacking the material that's bowing up, then the Z-axis may be bent/damaged. you may not be able to align it if this is the case. This may be one of the mechanical issues footstrap mentioned. If this is the case then aligning the nozzle at material height may be the only way to get it to cut at all.  

Chris Krug http://krugtech.com/
Maximum Up-time, Minimum BS