Just done my one this morning, 2008 1.8 TDCI. I bought a stainless steel plate with slotted holes and just loosened off the bolts on the pipe / EGR union and slipped it in. Didn't even have to remove the scuttle.
I've been a run of 50 miles or so today, and my initial experience is good - less smoke out the rear and a smoother power delivery throughout more of the power band.
And so far no EML, but I'm not counting my chickens just yet.
I, like you, was hesitant to do this, but my advice would be do it. If the worst come to the worst you can always take it back out, it's only a fiver you'll have wasted!.