I've ordered a ground anchor kit but instead of ground, I'll be bolting it to as big a chunk of concrete I can manage. I was thinking of mixing and allowing to set in a 13 litre galvanised bucket. This would create a 30kg weight. I will then drill into the concrete and fit the ground anchor with 2x Rawl bolts. I'll then chain two bikes to the concrete and hopefully have an undesirably awkward lump in the eyes of scumbag thieves. Also I've got a good shed with security hinges, bolt + good padlock and a wireless PIR that will trigger the main house alarm.
Any advice on the concrete bit would be appreciated.