@Maz44 If you are a UK/EU student, you can get a postgraduate loan for up to £10,250 which you can use however you like. You can go about getting that in the same way as the undergraduate loan, through the student loans company. However, this is not the same as a DSA.
In terms of DSA, from my understanding and experience you would have to be extremely lucky to get one if diabetes is your only issue, as it doesn't really incur any additional equipment costs. In addition, they rarely give it to you as cash - if its equipment, you buy the equipment that you need, send them the receipts and they reimburse you (at least in my boyfriend's experience).
Have you talked to the university you will be studying with? Many of them have scholarships for disabled students.