Col, that is the mistake I made. I got the actual visor on (eventually) but then trying to measure up the postion on the windscreen for the lettering becomes a nightmare. It's more difficult to fit and position the lettering while leaning over the bonnet than doing while it is laid falt on the floor. Fit the badges and lettering onto the visor, then using a fine mist sprayer, spray the windscreen with a water mixed with a little washing up liquid. Get another pair of hands and postion it as best you can. The water between the glass allows you to slide the visor around and/or peal it off if and refit if required. You just have to persevere with it until you get it right. Lastly, using a credit card, squeegie the water out from the visor making sure all little air bubbles are removed.
Hope that helps!
J