It can be anything. There are no fixed charges, but I doubt any solicitor would do it for less than £25 and most would want to charge nearer a hundred. Solicitors today charge around £120 an hour, so if they prepare the document as well as witness it then you can expect a hefty bill. See the link for more information.You should also remember that you can haggle. Just because a solicitor says he will charge £100 doesn't mean he won't accept £25.olicitors today charge around £120 an hour, so if they prepare the document as well as witness it then you can expect a hefty bill. See the link for more information.