Chocolate chip chelsea buns

I like chocolate. I like chelsea buns. Why not put them together?

300g cake flour (625ml)
2ml salt
50ml castor sugar
10g instant dry yeast
60g margarine

50ml lukewarm milk
1 large egg, beaten
100ml lukewarm water

filling:
60g margarine (can get away with cutting down on this)
50ml castor sugar
5ml cinnamon
75g chocolate chips (or raisins if you want, also much more chips can be added if you have)

Mix the flour, salt, sugar and yeast together.
Melt the marg in the lukewarm milk and add to the flour mixture, along with the beaten egg and enough warm water to form a soft dough.
Knead the dough well, until soft and elastic, about 10 minutes.
Place on a slightly floured plate, cover with greased plastic and place in a warm place (e.g. slightly warmed warming drawer) for 15 minutes.
Knock the dough down and roll into a 30cm square. Spread margarine on the dough and sprinkle with castor sugar, cinnamon and chocolate chips.
Roll the dough up into a roll and cut into slices about 4/5 cm thick. Place cut side down onto a greased oven proof dish. It is nice if the buns can grow into each other a bit when the rise again, to lessen the amount of area that goes harder on the outside.
Cover with greased plastic and allow to rise in a warm place for 25-30 minutes (until about double in volume). This is when you should heat your oven to 180C
Brush with egg or milk and bake for 20 minutes (check from about 15 minutes, sometimes they are ready early).

Ice however you like. A mixture of white and chocolate glace looks good.