If you are based in London and have been appointed as the Executor of a will, then you may be looking for help from a specialised Probate law firm in London. Registered Probate Lawyers can help with all of the steps involved in administering the Estate and distributing assets according to the will. Or in the absence of a will, in accordance with the rules of "intestacy".
There are a huge range of fees charged by Law firms for Probate. Ranging from Solicitors charging as much as £250 per hour PLUS a percentage of the Estate Value - to fixed fees from other Registered Conveyancers that range from a few hundred pounds upwards depending on the size and complexity of the Estate and other factors such as the Executors and Beneficiaries. So particularly in London where there are many suppliers to choose from - all of whom can arrange to visit you at home to explain their fees and services (a visit which naturally they should NOT charge you for!)
As a rule of thumb, if you are paying more than 1% of Estate Value then you are probably paying more than you have to. Make sure that such a fee is fixed and can't be added to. Realistically you should be paying a lot less for Probate in London.
There are two Regulators who regulate Probate Law Firms; the SRA who regulate Solicitors and the CLC who regulate Conveyancers who are now also regulated to carry out Probate. There are also plenty of unregulated firms who can help with Probate - but obviously you may be taking additional risks and you will not have a Regulator to complain to if things should go wrong. This is a List of Solicitors in London who do Wills and Probate
More on Probate in London