Change rear springs without removing strut?
 

As above, is it possible? Perhaps get the spring compressors on in the arch, then gun the main nut from above and then do the three top mount nuts etc?

Looks like a real pain to take the rear struts out from what I can tell.

Trying to change the springs with the struts still in the car is going to double or triple the amount of effort involved, take them out of the car. And be sure to use proper (and safe) spring compressing tools, these things can do a lot of damage if they slip loose during a swap.........