Bit of a head-scratcher for the panel:

I'm currently fitting out our en-suite, with a vanity unit thingy: see
http://tinyurl.com/42y7cm (or
http://img802.mytextgraphics.com/photolava/2008/04/28/bathroom-ffl1d0cc.jpeg)

Worktop and upstand is standard gloss laminated chipboard, about 1.7m
long (neither are fixed in position yet). Problem is that the wall on
the right is quite badly dished, which means there's a large gap behind
the upstand: see http://tinyurl.com/542dg8 (or
http://img801.mytextgraphics.com/photolava/2008/04/28/dished-ffl1gwcg.jpeg

The gap is 10mm at the widest point; the total length of the 'dished'
section is about 800mm. So what to do?

Ideally the wall level needs building up of course, but my plastering
skills aren't up to it and the work was done a long time ago so I have
no recourse to the guy who did it. (Anyway, it actually looks fine
until you put a straight edge to it!)

What I'd like to do is fix the upstand in position with the gap behind
reduced to 5mm - with the right filler, that will look OK, doesn't cause
the other end to bow outwards, and doesn't require *too* much bending
force. I don't want visible screw heads through the upstand, which I
suppose means it's No More Nails' time... but will that cope with the
tensile force? Is there a preferred type to use? Or could I pre-bend
the upstand I wonder...

Any thoughts on any of this would be most welcome.

Thanks
David