£15 is a very good price for 3 albums (Blah-Blah-Blah, Instinct and the live set from Boston 1988) plus the two studio discs contain 12" single remixes which have mostly never been available on cd before, and which are extremely hard to get on vinyl these days. And if you don't have these albums anyway... well, what are you waiting for?
The only negative points are that the live disc is not the complete concert - you'll need the KBFH 1997 release for the most complete best sounding version of this terrific gig. The KBFH version misses out "Your Pretty Face..." which IS included with the A&M sessions version, so between them you'd have the full show.
The other irritating thing is that "Shades" is the single version, NOT the original album cut. It's no different in mix but the single version fades out about 20 seconds from the end. So the A&M Sessions set is not, in fact, quite complete after all!
Your enjoymant of the studio albums may be tempered slightly by your personal opinions of mid 1980s productions. For me - I loved these albums at the time, went right off them a few years later when the production and overall sound ended up sounding rather dated, but have come to love them again. Blah-Blah-Blah especially is stuffed full of superb tunes (many co-written by Bowie which are way better than songs on his own albums of the time) and Instinct has a very solid sound. I feel that Instinct lacks enough variety, and too many songs sound a bit too similar, but there's more than enough good stuff here. The live album however, is superb!