Hmmm.. are you sure it was not the Control Zone you infringed? OK, at 3000 ft you would have infringed the TMA but unless you had a transponer on with altitude readout ATC would have paid little attention to you that far west. If they did not know your altitude they would assume that you were below controlled airspace and would not be bound to take avoiding action with other traffic. Heathrow has been on easterlies of late and they usually go down to 4000 ft that far out, but they can go to 3000 ft so it's not a safe place to be!
What gets ATC concerned is infringement of the CTZ because that airspace is from ground level and anything "unknown" in that airspace causes major problems and they have to take avoiding action with their traffic.
As mentioned already, who were you talking to? If you fly that close to controlled airspace it would be advisable to be talking to a radar unit.