This may help----there is Probate helpline tel .number
0854 3020900, I have found them to be excellent in the past.
You can get a copy of the original will if it has gone to probate, because the original is now a public document , there is a charge for this.
You may need to work out carefully what you really want to do about this matter.
It can be very expensive indeed to pursue the contents of an estate which have already been disposed of.,and pretty impossible to get the items back.
You might only want to confirm in your mind what has actually happened, and a will copy might do this for you .
As you mentioned the value of the estate in terms of cash was indeed small, and the possessions of the deceased were more of sentimental value than material wealth , I can understand why you are upset and rightly so as this was your Mother's demise.
However as mentioned in a previous post you may be well stuffed over the items, but you may want to know how it all happened, and I can fully understand that, so hope this helps a little.