That method can damage polycarbonate lenses the black tape absorbs radiated heat causing crazing and some of the adhesives can etch the lens when heated.
Eurolite and metro ultra are only about £10 anyway.
Metro are fine for the 244 and older lamps but probably not flexible enough for the 250 model curvature eurolites work fine though apparently.
http://www.motoring-into-europe.co.uk/download/motorcaravanning-matters-article.pdf
The key thing when fitting either is you need to be at eye level with the dipped bulb to align them correctly and double check against a wall.