I have Michelin Pilot Sport 4S: 275 35 20's on ET35 10J's (no more spacers) and have it lowered on H&R OE Sports Springs (1BE S-line sports suspension- not sure if that means anything after you have changed the springs)- I first upgraded from stock 255 35 19's to 20's & kept the sidewall at 35 because it was hitting the speed bumps after lowering when still on the 19's and also because it was really hard-ass in the seat.. so now with the 20's & addition of a set of rubber coiled 'spring-assistors' fitted inside the springs this has restored the comfort again and also never grounds on speed bumps- having said that, it's absolutely right on the clearance limit is it touches the arches occasionally on cornering when on bumpy rough tracks. The speedo is only 2mph off when at 30- but I go by Waze for speed accuracy anyway.It's because the 20" wheel the OP has is 11 inches wide. The 20s in the OEM wheels are 10 inch I believe using 265/275 tyres, so the tyre width is correct in this case, just not the sidewall.
However, I may go over to try 275 30 20 next time around, as hopefully the comfort won't be compromised too much by losing the extra 5 of air on the sides and this would probably remove any possibility of touching and visually should look fine, as there is no gap at all atm- as you can see here.
Edit: I've now made the switch to 275 30 20 (from 35) and it is perfect- and the speedo is accurate plus there is absolutely no rub- even on rough ground or when turning and braking, and my initial concerns about grounding over speed bumps and harsher ride were unfounded as does neither- so with lowered springs, ET35 10j 20" wheels the 275 30 20 tyres are definitely the best solution.
(This pic is of the 35's).