If you want to get rid of them all at once, I’d contact a dealer e.g. Simon Watson at the Aviation Bookshop or Andy Doran at the Falconwood Transport Bookshop. 

If you want the hassle of selling them yourself, then just list them on Ebay for a minimal amount and see what happens.

If collected from Farnborough they are unlikely to be very valuable, as sales brochures are usually short and don’t generally have any unique information you won’t find elsewhere. Some specifically popular aircraft types might be collectable I guess.

If you have any brochures for rare items like aircraft, engines, radars or missiles that didn’t get produced en masse – like TSR.2, Rotodyne, etc.  or even designs that were never built – this kind of material would sell well to people on my forum (secretprojects.co.uk).