He probably [Mod - Happy Thoughts]umed your were IFR, as VFR can only depart Heathrow under particular conditions, and your route is an IFR route, coupled with the fact you would probably be in Cl[Mod - Happy Thoughts] A airspace at 6000ft, where VFR is not allowed. IFR traffic usually makes contact with tower on final approach of the runway in use.
Re: sam thx very much for the answer, that makes the picture clear now. I just applied for flight training with vatsim-uk today, need to learn from basic..