Don't fit pattern TREs, they are all universally shite. Whilst GM ones are £25 a pop, there are worth the extra.
Not sure you'd notice the different between B4 shocks v Sachs and similar. Remember, B4 is Bilstein's OE replacement, not a sports shock. I use Bilstein because they seem to last a bit longer than Sachs or GM, yet similar price. *ANY* shock will feel stiffer that what you have, as yours will be getting tired.
Unless you drive spirited, and I've never known you to, no need for lowered, stiffer springs. You'll just ruin its mile cruncher ride. And clearly you didn't drive that C Class spirited, else you would be pointing out how crap it really is. TBE is on standard springs (can't remember brand, but one of the ZF ones), and for a reason.
Those tyres have loads on. The only issue is the inner edge wear. So I doubt you'll be putting new tyres on this Spring.
Given that you don't touch your car for years, I'd also recommend you give that ATP shite a very wide berth.