Refitting Fulvia headlamp switch

[9JOT]

I'm really struggling to refit my Fulvia (S3) steering column headlight switch. The small rollers which (I presume) operate the self-cancelling mechanism appear to be pressing too heavily on the steering column itself and this in turn is making it impossible to seat the switch properly in the alloy casting in order to locate the large brass locking ring.
I've seated the small metal tab on the domed metal casing which ensures the switch is in the correct orientation and so I know that's not the cause of the problem.
Is there some significance to the amount of shims/washers which sit under the retaining collar which locates the switch into its domed metal casing?

[9JOT]

Pronlem solved! The lesson to take away from this is don't assume the switches on a RHD car have the same orientation as a LHD car...
I'd been using the standard Lancia handbook for reference which of course depicts a LHD car. It appears that on UK models Lancia moved the headlight stalk to the right hand side of the column and it's been so many years since I last drove the car I'd completely forgotten how it all went back together.
Every day's a school day as they say.