Since the UK is going down the American route of "sue, sue, sue", third party insurance is a MUST! It's okay putting notes on models saying "do not touch", but that has no standing in a court of law...
Anyone who runs a model of any type (IC, fast electric, steam, sail, scale, whatever) is just asking for trouble without insurance, and with such a low premium (literally a few pence a day), why would you want to take the risk?
Regards
Eddy