Thanks fo ryour reply.
If the 2 sets of house Deeds ar enot registered, you would need to apply to the Land Registration for "first registration, based on lost deeds".
On making the application, you will need to provide as much evidence as you can that you/your Mother own the respective properties. Ideally, this would comprise copies of any Deeds you may be holding/Solicitors letters from the time you purchased/current and past Council tax invoices,a sevidence that you are residing at the property. Barclays should also provide to you a letter or certificate confirming that they were in receipt of the Deeds, but these have been subsequently lost.
The Land Registry are pretty decent when considering such applications, and you should not have any problem in registering both properties.
I set out below a link to the Land Registry website, for further information on the application-
There will be a fee payable to the Land Registry for the application, and at the very least, Barclays should be offering to pay for this, as well as for your Solicitors fees in making the application. (A Solicitor is likely to charge you approx £400 plus VAT for each application).
I hope this assists, but please let me know if you require any further clarification.