Dropping 35mm on the front and 30mm on the rear will for sure give you clearance issues regarding speed humps,kerbs,ramps etc. I have Swift Spec R lowering springs which are very highly regarding on the US 370 forum and lower 30mm front 25mm rear. I had to remove the front chin spoiler and tyre deflectors otherwise they would be mangled. Speed humps still have to be taken at an angle to avoid scaping. I actually think the front of my 370 looks tidier wihout the chin spoiler and tyre deflectors.
Once lowered you will defo need spacers. I eventually settled on 25mm front and 20mm rear which takes me flush with the bodywork and yes I did get slight rubbing on the wheel arch liner. Once the springs and spacers were fitted I then had the geo done and found all but one corner was in factory spec so decided against camber arms at that stage. That was around 6000 miles ago and have got to say tyre wear is quite even.
You are welcome to pop over to Leicester and have a look at my 370 sometime. I'm 10mins from junction 20 M1.
Also would thoroughly recommend CS top chaps Mitz and Andy who know their stuff!
Cheers,
Scotty