Thanks Guys, especially Andrewr and Chris ........... Securing a hardtop at the boot with bolts would seem sensible along with the clips on the windscreen .....
I remember Richard Thorne had a couple of Aero's for sale and they both had factory hardtop options

... So having just had a look at his site both of the cars have the same fittings on the boot.
Must take a look under the carpet and see if I have anything extra like Geir

Cheers ................ Pete