I have coilovers on, and it is a *very* hard ride! I have to avoid certain roads, or take them very slowly if I don't want to do real damage.
The advantage is you can raise and lower the car to the perfect height - its labourious but it does mean you can set it just right

I live on a road with speed bumps all the way down, and I have to do 10mph or less the whole way - but I am as low as I can go without scraping (just), and if I ever did start to hit tarmac I could reset the height so I could clear it.
Lovely handling on a good road, but can get a bit skitish on bumpy corners and roads....
I would hope that no spring would snap, but if one did on a coilover I'm sure you could get just a spring for coilovers too...
Plus springs/shocks will tend to be cheaper than coilovers I think
Do you ever end up near Leicester? I'd offer to take you out for a drive in mine and you could see what coilovers are like....