If you have a mortgage there may be something in the t&cs - ISTR asking once on mine about running a business (non CNC related) from home. Wasn't a problem for a 'paperwork only' type business but they were a bit iffy about anything involving keeping 'stock' (of whatever value) on the premises. Not really sure why...

The home insurance said much the same. I suspect anything over and above paperwork might be an issue for them - but perhaps they could exclude the shed from the policy or something. Dunno.

Only other thing I can think of is that a fire extinguisher on hand is a good idea in any case as are proper electrics for the shed.