Greetings Simon-
Pickups have microphonic qualities when something inside the pickup becomes loose and vibrates, causing them to function like the diaphragm of a microphone. Some pickups are microphonic from the moment they are made, and some pickups become microphonic over time. Today, almost all decent replacement pickups are "wax potted," which means that they have been dipped in wax to seal the windings and keep parts from vibrating. I find that even the less expensive pickups ($40-60) by WD, Stewart-MacDonald, All Parts, etc. are very good, and the variety of DiMarzio and SeyMour Duncan in the $75-$90 range is amazing.
By the way, I'm surprised that a Fender reissue would have this problem! Doesn't the Tele Thinline have the humbucking pickups with the staggered 3-plus-3 polepieces? They might be a little difficult to replace, as they are not the same dimensions as Gibson humbuckers. You might also want to consider a new pickguard, cut for Gibson-sized humbuckers, while you're tearing the little beast apart.
Best of luck!
Douglas Baldwin, coyote-at-large
coyotelk@...
coyotelk@...