Basically as per the title, I've got a 97 20vt non-aircon with almost new suspension all round and a 2000 20vt6 which could do with a freshen up. I have some memory of a mention that the suspension struts aren't compatible. I would appreciate your wisdom.

Ta.

I know the 20vt 6 springs are different...

Lower arms, drop links are the same, shocks are the same but spring rates are different!!

Yes, you can

They will physically fit, but as Marco says, the spring rates are very slightly different

However, you'll probably find that the newer (but slightly softer) springs off the non-aircon car will still be better on the 20VT[6], as the damping is better controlled

Its an easy enough swap - just try it