You can try the Probate Registry local to your nan - phone them first to find out if they have a publicly available copy of "Willfinder". You will need Nan's full name, address and date of death. Once you have established whether there was a Grant of Probate you can then request a copy of the Will from the registry.
Or
write to Postal Searches and Copies Department
York Probate Sub-Registry
1st Floor, Castle Chambers
Clifford Street
York YO1 9RG
give same details above and enclose a cheque for £5.00 to HMPG. If probate has been granted (I assume it must have been because there is a property - unless that was jointly owned with someone who inherited by survivorship) they will send you a copy of the Will and Grant.