Iklboo, I started at the beginning with Ian Rankin, Knots and Crosses I think, but it might work better starting a few books in. I thought the 1st 3 were ok but wasn't sure what the fuss was about, didn't like no 4 much, and then really enjoyed The Black Book, no 5 at the time, and caught up to the rest at the rate of one a month (this was a few years ago long before motherhood when I averaged out at more than 1 book every 2 days). I saved the most recent The Naming of the Dead to read when I finished work but before baby turned up, correctly expecting he'd be late. So The Black Book or his real breakthrough in terms of sales and fame, no 8 Black and Blue, might be good ones to start with. My personal favourite now is probably Fleshmarket Close, but that's because he deals with immigration/asylum from a political perspective I'm very sympathetic to, however, you don't have to be political to enjoy his work.
Yes, Massey's series starts with The Salaryman's Wife.
Mark Billingham and Simon Kernick both set their books in north London, though I understand Billingham is also planning to do something different from his series featuring Tom Thorne. I guess that makes sense after 6 books but am sorry I only have one more to read.
Other suggestions for those who like British police detectives - I think John Harvey writes really well, and I also normally read Peter Robinson's Alan Banks books as they come out, although I still have 3 early ones to catch up with. Stephen Booth writes a series set in Derbyshire's Peak District. Patricia Hall writes a series I buy in hardback but is now published in paperback again (some of the middle books in the series weren't) - start with what you can get hold of - and Allison & Busby, her publisher, have also reprinted all Stuart Pawson's Charlie Priest series, a little lighter in tone than many of the other books in this vein I and other posters have mentioned - first and one of the best is The Picasso Scam.