What do you know about probate services?

A member of my family has written a will and the company they have done this with offers a service which cuts out the need to go through a soliciter when you die and sorts out your estate for a fixed rate,payable in advance,instead of the percentage of the estate that a soliciter would charge ,which presumably is much more than the fixed fee. i don't know any thing about these things,is this a good idea? It sounds like a good deal,are there any catches?