I know it's not free but £1.99 Check Mend
I don't think there are any free ones for the uk.
Common symptoms of blocked stolen or lost mobile phones are:T-Mobile & Virgin Mobile
When a SIM is inserted in the phone it will seem as though the mobile is working and will show that you have reception on the network.
However if you try to dial out although it will seem that the call is going through, you will hear a number unrecognized tone.
If you were to dial the number of the SIM card you entered, the mobile would not ring when called.Vodafone
The phone will again show reception but when an outbound call is made it will repeatedly fail. You will only be able to send text messages.
Note: Sometimes a phone will work on the Vodafone network for calls going out but the SIM will be barred after a while.
If you check it on other networks you can find out if the phone is barred as it will display the symptoms described for the other networks.O2 & Orange
On O2 and Orange the SIM will say simcard registration failure, will have no reception and no network operator logo will appear.