There is nothing wrong, per se with handwritten accounts.
I would suggest you obtain a copy of the Will and a copy of the Grant of Representation from the Probate Registry. You can write to the Postal Searches Department at Leeds - details here:-
http://www.justice.gov.uk/courts/probate/copies-of-grants-wills
Once you have obtained the copy Grant it will say what the gross estate was (ie total of all assets) and what the net estate was (ie assets minus liabilities). See if what is said on the accounts tallies or differs significantly. If it differs significantly, you should ask further questions.