This whole Will location thing is interesting. Somewhat naively I thought that if a Will pre-dated Probate (1858) and survived they were in the National Archive and therefore online either at TNA or via a pay per view website.
Anyway having accessed said pay per view website (TG) they have this very helpful and succinct bit of info:

Locating Wills

Wills proven in the Prerogative Court of Canterbury are now held at the National Archives in Kew.

Wills proven in the Prerogative Court of York are currently held at Bothwick Institute, part of the University of York.

All other wills up to 1858 are held in local record offices across the country, apart from those in Wales from 1521, which are held at the National Library of Wales in Aberystwyth.


Also Wills proven in the Archdeanery of Canterbury are not in TNA but in Kent Record Office just to be helpful!