As you may be aware, your standard home contents insurance policy can cover your household possessions against a number of perils including loss, damage, fire and theft.
Home contents policies are generally designed to cover items in a typical household, e.g. floor coverings; curtains; furniture; household appliances and electronics; household utensils and crockery; garden and DIY tools and equipment; clothing; and sports and leisure equipment that may include pedal cycles and musical instruments.
As you will note, there is no mention of specialised items such as 5in gauge model locomotives, pillar drills, lathes, milling machines, sit-astride riding cars, etc. There is a possibility that such items that you cherish and use in your hobby are not covered by your home insurance, so if you are in any doubt you should check with your provider.
In addition to this aspect, home content policies may also have a restriction of as little as £1000 on the sum insured contained within domestic outbuildings e.g. a shed or garage. It is worth bearing in mind that this is also where you are likely to store your lawnmower, hedge trimmers and other garden, outdoor and DIY equipment, which can result in £1000 not going very far in the event a shed or garage is broken into and these items are stolen.