Graham, well I just popped down to the two rail terminals and the cripples area, theres over 200 wagons here at the moment, guess what, not a single FFA/FGA, pretty much everything else in spades but not these, however as mentioned before I'm sure I have these at home, though they may not be exactly the areas you need, I just banged away at anything I thought I might need in the future. I will check when I get home off shift later tonight for you.
Regarding brakes, seems tread brakes are not as old fashioned as I thought, at least 60% are still tread brakes, a quick run over what we have seems to show two types of bogie, fabricated and cast, I've no idea what the official designations are, they're not stamped on them anywhere. All fabricated types appear to have tread brakes on both sides of the wheel if I recall, will double check this afternoon. The cast bogies have both types of brake, older bogies built 1988 or so have tread brakes but only on the inner side of the wheel, none on the outer, in other words the brakes are trying to force the axels apart in the longitudinal plane. Later bogies, 1993 ish had disc brakes on the axel. None of these are on FFA/FGA wagons but I think its the same bogie so it looks date dependant on which type of brake is fitted and being as the bogies come complete with all the brake gear self contained, it is possible I presume to simply swap one type for another.
Clamp locks, we call them twistlocks or fixed cones
, there are two types twistlocks are just that, the cone is able to rotate and lock the box to the wagon, the fixed cone are a more different kettle of fish, they are specially shaped, unlike the twistlock which is a pure cone, the fixed cone has a bulbous top, it does not rotate but relys on the bulb to stop the box from coming off. In technical terms the underside of the bulb will catch on the inside of the pocket. The theory is that for a box to fall off a wagon it will have a rotational moment and will slide toward the rotation moment, in doing so the cone will become off center in the pocket and catch the box, doesnt always work, read the RAIB reports on Grayrigg and Cheddington where empty boxes have been blown off trains in high cross wind conditions!, I can provide a link if your really interested, actually RAIB reports are very good and often detail specific parts of railway vehicle running gear, the one on the Ely stone train derailment whent into quite good detail about that type of axel box and springing, lots of detail shots and sketches, good for modeling. Anyway, back on track, the fixed cone is designed to allow a box to be lifted in the vertical plane but any side movement or rolling moment will cause it to grab the box pocket with the underside of the bulb, I think a photo would explain it easier LOL, will supply images of both types tonight either way.
Looking on the web I see that the FFA/FGA runs with twistlocks and not fixed cones so can provide images of those easy enough, the bogies are cast but have the spring plank protruding through their midships and rotating bearing cups on the outside, I know I've seen these so pretty sure I have photos at home, if not I can get some at work when they do get here...if they're still in service....or at locations on the line where I know they stop for signal clearance (Clickett Hill etc).
Addendum, just thought, the above mentioned RAIB reports and the recent Marks Tey derailment might detail FFA/FGA wagons, don't have the link at work but will try and Sherlock it for you in a moment.
HTH...for the current moment.