Kevin,
You need to get the cracks investigated and then most probably repaired.
Hairline cracks in a plastic material indicate that undue force and stress has been (or is still being) applied to the structure - it could be that the panel was stressed when the van was assembled, or you've had a load of stone impacts causing the cracking, or some other on-going stressing of the panel.
Caravan body panels are either aluminium, thin GRP sheet, moulded GRP (thicker than GRP sheet), or Acrylic-capped ABS
Fibre-glass and GRP are the same material - a polyester resin based product that uses woven or chopped glass mat to provide structural reinforcement.
I believe it was Abbey in the mid 90's that pioneered the use of thin GRP body panels, rather than the traditional aluminium panels. The advantage of this GRP material is that it can be repaired using conventional car bodywork fillers.
Likewise thicker GRP mouldings - like your front panel - can also be repaired with the same car bodywork fillers. Most cracks in this thicker GRP material only extend into the top Gel-coat layer of the resin (it's the first layer of resin before they start adding the glass reinforcement) and the body of the GRP is still intact.
Acrylic capped ABS is more difficult - plastic car bumpers are made of this material - which uses the acrylic cap to give a smooth finish to the matt ABS. Things made with capped ABS - like some caravan wheel spats - are much more difficult to repair - it's usually a replacement panel.
Your front panel:
It is most likely a thick GRP moulding that can be successfully repaired with car bodywork polyester resin.
The hairline cracks will most probably only be in the "clear" Gel-coat and the repair will be as strong as the original panel.
Robert