I have just got new house insurance following the extension and modernisation of the pad. I also included the garage and contents but was specific about the bikes and managed to get coverage of £15k for bikes and tools etc excluding the motorbikes which are covered themselves anyway.
just needed to add some side bars to the garage door that's all.
The people insuring me came in cheaper than Aeon (who we were with) and the house went from 3 bed 1 bathroom to 4 bed, study 3 b/rooms and extra bikes etc in the garage!!
pm if you want my insurers details.