Thanks for your advice, I pushed the microswitch in with the flat blade screwdriver a few times, then got my friend to hold it in. Nothing changed. We repeated this around five more times and still got the flashing light....
then as I was driving back around 10 mins into the journey at a steady 60mph on the dual carriageway, the light stopped flashing. I haven't had time to try the roof yet but will report back any findings.