Really useful post, thanks.
I have very recently gone BPU, Spec as in my sig.
I got it done at Whifbitz last month.
Since then I have done over 3,000 miles all round Scotland and enjoyed every mile. I wish I had done it earlier (had the car nearly 4 years now) TOTALLY different drive now.
Having read your post I WILL be changing oil religiously.
I have NGK Iridium spark plugs, not sure how many miles these are supposed to last.
My Supe has now done 64,000 miles so based on your experience hopefully I will soar into 6 figures over the next few years with no issues (crosses fingers)