It won't work Jon - if there is a mortgage deed in your name which has been signed by you and is properly authenticated, that is proof of the debt. Even though there may be procedural errors in what the BS have done, or not done, no Judge is going to throw out their case because of these though the BS may be penalised by loss of some interest as a "punishment" As far as notifying you of the sale within 28 days, note that this can be your last known residence which is..........the repossessed property! Unless of course they have other address for you.(posted 8157 days ago)The Theft Act bit - non starter this - County Courts dont deal with theft and I doubt very much the Police will involve themselves if you report it. The whole matter is a Civil contractual one and the evidence required is not as strict as the criminal courts.
I hope you haven,t filed that defence! See a solicitor - don't try and go it alone otherwise you may dig yourself in a lot deeper than you can shovel yourself out of and more importantly, you may increase the costs to the other side which you ultimately might have to pay!
Get proper legal advice on this - you have enough time, but if any time limit is upon you, simply send a letter to the court to ask for more time as you are seeking legal advice - it will normally be granted.
Good luck!