Andy,
Units are available individually but do come as a fully assembled kit so yes

Sometimes the outer top mount (the bit you see in the engine bay) is done as an exchange if we have none in stock.
But being customer focused Im sure if someone said they already had the springs and or or top/bottom spring pans etc then it wouldn't be a problem.
What I know he wont sell is the inner top mount without the strut as the two are designed to work in tandem together, with the way one sits on top of the other, to even out the extra load placings.
HTH