Skoda Octavia knocking noise behind passenger glovebox area

My Octavia has had a knocking/creaking related to minor road undulations since purchase (2nd hand Feb 2013). It has been back to main dealer 6 times and still it is there. Last visit they identified it as a "broken weld on a bracket which is related to if the car was to be a left hand drive model". The technicioan said he had to "tac it up "?? and was convinced he had fixed it. In fact the knocking seem to has been reduced by about 60% but not eliminated. Dash has been out many times, windscreen relaced and rebonded. Such a shame - brilliant car. Any thoughts?