Last year I replaced all 4 shocks and mounts on my 850T5 and although it improved the ride slightly it still feels very hard, you can feel every bump.
I have just got back from putting the car through it's annual inspection, similar to the UK MOT, and they told me that the suspension was only working at about 50% which seems keeping with the ride quality.
Are a set of new springs going to give me that extra comfort that i'm looking for?

 

I'd start by checking tire pressure. Did you push them over 36 PSI? To note, the OEM Sach/Boge struts are actually pretty firm and 850s can ride firmer than most cars. What did you use for the replacement parts? I've never heard of springs going "hard" - does your car appear to be riding low - usually springs can either break (typically at the ends) or sag. Not sure is meant by "working at 50%". Did the shop check other areas like control arm bushings, sway bar end links, spring seats - but there I'd expect other symptoms like clunks or odd handling behavior.

 

People don't buy new shocks and springs to make the ride soft. So no. Springs would be a bad idea. In theory, softer springs could be fitted to any car, but in practice, there's no demand for that, and nobody ever does it. Few people who fix cars professionally are smart enough to do that as a one-off, so my advice is save your money.

Tires, however, could be a more fruitful area to explore. It's possible a different tire that is praised for a smooth ride could be noticeably better.

I also don't like the phrase "working at 50%". They are treating you like an idiot, just hoping you'll come back and they can claim they replaced something and charge you. When you talk up schemes like that, you don't really even have to replace any parts. You can just pretend you did.

 

Gotta agree with Fire so far. The reason for upgrading or replacing springs is to have the car more planted on the ground and increase handling. Don't let the shop swindle you. Like Fire said I would look at good tires next to complete the package. "Working at 50%", lol.

My T-5r has Koni-fsd's and Eibach springs all around. It is quite firm and great in corners. In my opinion it can be harsh over bad roads, but not terrible. I need to put tires on it badly cause the front are bald and the rears have lots of tread lol. I guarantee that when I get around to it, my car will absorb bumps much better.

Tires are as important as shocks/springs. Probably more because if your car can't grip the road, shocks/springs won't do a thing.