AJ
To be clear, you are receiving a payment labelled as "money because you are severely disabled"? If you are then you are still barred from claiming UC and you should contact your Local Authority to tell them that you are receiving the Severe Disability Premium.
Being in the SG enables payment of the Enhanced Disability Premium, this shows as the "Disability Income Guarantee" on your ESA entitlement letters. This Premium does not bar you from claiming UC.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems