As above, will i need a spring compressor or a castle nut tool or anything like that or is it as simple as pulling the strut out and swapping the bits over?

you'll need a castle nut tool to remove it from the top of the topmount i think, not sure how much tension the springs are under?

You will need spring compressors really, i think its been done before but i wouldn't like to attempt it without. ALso a special tool from GSF to undo the castle nut.

Yep Just finished doing it now, gotta love doing the topmounts in the dark