after having both front fogs broken now, one of which was by part of a brick that came over from the other carriageway and I was lucky to see it and slow enough for it to bounce off the drivers wing and then down into the fog light, I've been looking around for something to provide a level of protection for the lamps. I have a replacement front bumper that needs fitting at some point and it has nice new fog lamps in it and I didn't want to fit this until I had some sort of solution available.
Checking around on ebay I found this
so I emailed the seller who was very helpful. They are 80mm diameter and after discussions he modified the lugs so they bent outward at 90-degrees and had a 5mm offset to hold them clear of the glass.
I've now cut a recess into the black fog light housing to accommodate the lugs and shortened them to fit into the available space and they look very good, hardly noticeable at all. I cut the rebate at an angle so as to get the smallest gap around the protector given the curve of the housing. Depth of the rebate is approx 2.5mm to 5mm, no worries if you don't cut too neatly as it'll be hidden behind the lug once the protector is fitted.
I've only done a first fit so far and it looks fine to me, plan to fix the protectors to the housing with a little clear silicone RTV or araldite and then add some silicone behind the tab to fill the gap to the fog light glass, to absorb shock rather than transmit it directly into the glass itself.
With a gap around the protector, dirt can get behind and onto the fog light, but the housing is easily removed for cleaning so am not too concerned. I guess it could be sealed with silicone, but that would also need the same around the fog light/housing as well, since there is a slight gap between the housing and glass in any case, but condensation may then become a problem instead.
hope this helps someone else