Rob, the method you are suggesting will be fine for 90% of the suites you find in customers homes. hopefully this suite won't be one of the other 10%

I would clean an area in a non-seen area first then compare it to the rest tof the suite if its the same then continue.
this is just my advice and I'm no expert so it might be worth contacting either Furniture clinic or LTT
as you can see Furniture clinic has some friends on this site who will testify that the sun shines out of Bens bottom

and are a little biased
I'm friends with neither of them and I've done courses with both companies, LTTs course was without a doubt the most thorough and professional, after completing the leather cleaning course with F/C I did'nt feel confident in my knowledge of leather to be able to go out and charge for my service, so booked a course with LTT.
I wouldn't normally make this sort of comment but something needs to be said to redress the balance due to the obvious friends that F/C has, I don't want to make this thread into 'LTT-V-Furniture Clinic' so I'll say no more.
I'm sure Rob you an intelligent gentlemen, so make your own mind up who to call