The Probate Department of the Principal, Registry of the Family Division, First Avenue House, 42 � 49 High Holborn, London, WC1V 6NP.
Telephone: 020 7947 7000
is the place to start
If you go there you can look the will up in the index for free and get a copy for a few ��. I'm pretty sure they also do a mail order service.
A bit more info if you want to do it by post: write to ;
York Probate Sub Registry
1st Floor
Castle Chambers
Clifford Street
York YO1 9RG
In your letter you should provide the full name of the deceased, date of birth, last permanent address and date of death. The fee for a search (which includes a copy of the grant and/or will if a record is found) is �5.00, payable to "HMCS". If you wish a search to be made for a period of more than 4 years, there is an additional fee of �3.00 for each period of 4 years after the first 4 years.