Yes they are. 0800 numbers are completely free to call from a Virgin Mobile phone. Calling any freephone number – any 0800 or 0808 prefixed phone number – from any Virgin Mobile, other mobile or landline in the UK is completely free of charge – you won’t be charged a penny and the call won’t eat into any free minutes allowance you have either.
0800 numbers have been free to call from landline phones for decades – they were first used in November 1985. But in the last 20 years mobile phones have become extremely popular so Ofcom has recently reformed the way it regulated the British telecommunications sector to ensure that calls to 0800 numbers from mobiles and landlines alike are now free of charge.