What springs do I have?

[UFO-666]

Hi all, just wanted to pick some brains to see if I have a workaround for my broken spring problem. 

So basically I bought my S-Max individual 2009 (2.2 diesel) about 5 years ago and I thought the stance looked lower than stock so assumed it had lowering springs on. I've been getting some knocking on the rear so took to garage and they said I have a snapped spring..... Now the problem... They said it's so rusty they can't tell anything from it so don't know what size spring it would need. I haven't got the cash to get a whole new kit so just want the rear done. So my question being, is there any way of knowing? 

I was thinking maybe if you could measure the standard distance from floor to arch on stock and then measure my good side rear to find the difference? 

Thanks in advance for any responses 😃