This should work, but might not be ideal - get a PAYG sim with maybe £5 of credit on it (I suppose not everyone has them lying around) and activate it with that (It needs to be on the same network that the phone is locked to) and then disable all the 'phone' functions. It should then function just fine.

This should work, but might not be ideal - get a pay-as-you-go (i.e., non-contract) SIM with a small amount of credit on it (I suppose not everyone has them lying around) and activate it with that (it needs to be on the same network that the phone is locked to) and then disable all the 'phone' functions. It should then function just fine.