I've bought some squareish trailer type rear light clusters which have to be mounted on a plinth to make the rear face vertical(?), ditto the foglamp. I am tempted to buy a set of conical type (BMC Mini front indicator shape) rear lights, as they don't have a "face" do they have to be mounted on a vertical surface? would one of those with a suitable bulb be OK for a rear fog? and vertically mounted?. Have looked at the IVA manual but cannot see what bits would cover this.

As far as i know, its just the Fog Light and Reflectors that need to be vertical. I think you are ok with all of the other rear lights.

Only the fog has to be perfectly vertical, in reality one of the more sensible rules-to avoid blinding drivers behind you!
Just get a single fog and hang it off a bracket below the rear for iva, then connect the cluster ones up later

You can't use a Mini/Land Rover type light as a fog light (at least not for IVA test itself) because it is not a Fog light - I think they have an F marking (someone will correct me) and have different shape of reflector or something to direct the beam back in a certain pattern.

Is this the style of indicator your looking at if so I have a pair for sale.

Bought them for a previous kit which I no longer have.

http://www.cbsonline.co.uk/mini-style-indicator-amber-pair-rl26-1516-p.asp