Thanks for the helpful replies ( and one or two others). But Dudeness's question is not answered. I fly a C525 -what is most helpful information as regarding aircraft type:
1. C525 - do ATCOs know every ICAO code?
2. Citation Jet (could be anything from 510 to 750)
Also, if it is for wake spacing, why not just ask for a/c wake category? At least pilots would then know why the question is being asked.
It is the ICAO code of the flight planned aircraft which we have infront of us on our strips, so please use that.
I'm afraid asking the pilot for their wake category as apposed to their definitive ICAO aircraft-type-code is a plain stupid idea. The categories' names and limits differ depending where in the world you're flying so whats the point of making it even more confusing? How about you simply answer the question of what type you are and let us separate complying to the UK minima using the UK wake categories.
Enjoy your flight into Heathrow! I'd be very intrigued to see into the flight deck during a single pilot approach into Heathrow.