I think the key phrase in your post is "
I have no intention of selling these if I can't get a reasonable amount for them". There's definitely an active market for photography gear here in the UK, from vintage film cameras and lenses through to the latest digital models. Stating the obvious, though, pricing has to be right (and in line with condition). Equipment is only worth what someone will pay for it, regardless of what the seller
thinks it's worth. I've seen folks in our own Marketplace and on eBay listing quite well-used items at not much less than discounted deals for new. A $1,200 lens that has been used for a year or two and is in very good condition isn't likely to find many potential buyers if it's priced at $1,000, but would sell instantly at $600. The
fair market value is somewhere between the two. A seller who's motivated will likely accept a slightly lower price than market average and sell faster. You can often tell, looking at some of the Marketplace listings, who really wants to sell and who doesn't, simply by looking at the pricing
Some items, of course, sell better than others. Your FA85/1.4 will be a breeze to sell should you decide. But still, the market sets what it's worth, not the seller...