Welcome and well done. Glad it was that "easy". If really full of crud, you would of thought it would be almost completely blocked up and hard to shift.
Later facelift cars like ours are a son of a female dog to get the matrix out, so this will help if I should need it. Touch wood mine works pretty well.
Some have suggested orange juice and then a flush, which may be acidic enough to clear deposits. Maybe pour some of that in. Leave for 30 minutes, add some Vodka and drink.
Of course no driving afterwards.
Maybe this should be part of the standard service - very 6,000 miles back flush heater matrix.
