To 99.99% of people old computers are obsolete junk. There are many computer collectors that would not recognize a million dollar work of art in a trashcan either.
Anything non working and not worth fixing I trash. If I think somebody might be able to use an item I don't want I either sell it or give it away (depending on the percieved value and effort needed to sell/ship something). At the end of the day if nobody wants it and I am tired of tripping on it I recycle or trash it.
I would think an A500 in the UK is like a C64 here in the US, very common and it is hard to give them away unless they are complete working systems. With 20 million or so C64s made they will never be rare anyway.