A little update.
After going in and speaking to my manager today he said I could self isolate myself without the government saying I had to but would have to take my holiday/sick pay.
If I was to get a doctors note I would be on full pay.
So I did the e consultation for my local doctors surgery and asked whether I should or shouldn't be isolating as I am a type 1 diabetic, he promptly replied saying as I am in a high risk group I should self isolate for 12 weeks as the government have outlined and gave me a doctors note. Peace of mind for me.