I have absolutely no reason to suspect that Thames/Heathrow controllers have any aversion to "Tiddlers" as you call them. We normally get a superb service.
There is one posting above, from Heathrow Director which includes the expressions "clockwork mice" and "I wonder how many GA pilots pay for the service they receive?" which does show an attitude which some in the GA community think is widespread in NATS, but my experience is quite the opposite.
Indeed, I am an IR instructor based at Biggin Hill and I have to take IR students into the airways system.
You can imagine how popular is a PA28 or Cirrus going from Biggin Hill to Gloucester or Cranfield IFR! But I need to do it to cover the syllabus.
I have never had the slightest hint from the TC controllers that they are inconvenienced by our presence, though, having played on the simulator at TC, I know just what a pain it is for them.
I have nothing but respect and admiration for the TC and TA controllers.