Thanks guys,
Unfortunately my mdf is too thin to use that tool. What I am gonna do is get some 10mm MDF and a test bit of tmounting to see if i can trim it with a very shap knife. Either that or go to halfords and get the 10mm chrome trim they sell.
It also turns out that 10mm mdf is pretty hard to find in the uk too! It is usually either 9 or 12mm.