Wow...lots of names to go through.
I discovered the Brian Freemantle/Charlie Muffin series late last year and went through the whole thing in a couple of weeks (and was amazed to see new titles are still coming out) - would definitely recommend.
Discovered a fairly new author through my library (think his thrillers are new, looks like he also has some PI titles): Adrian Magson's Harry Tate. He's former military intelligence, transferred to MI5, then he gets burned in the first book - which reminded me a bit of Six Days of the Condor...
Red Station - Adrian Magson
First in the brand-new Harry Tate thriller series - Having been made the scapegoat for a botched drugs intercept operation, MI5 officer Harry Tate is dispatched to 'Red Station', a remote outpost in the Balkans, ostensibly to avoid press scrutiny, but where in effect the security services send 'problem' agents they'd like to be rid of. But the outpost is thrust into the international spotlight when troops begin massing in the area; and, as the situation becomes increasingly dangerous, Tate discovers the real, truly shocking, purpose behind 'Red Station' - and decides to fight back . . .
Also really like Brian Haig's Maj Sean Drummond, though I guess those probably fall more under political thrillers.