Hi Stuart,
Your gp practice will know which inoculations you need when travelling to Namibia, watching tv documentary programmes like GP's Behind Closed Doors some have to be given months before travelling so I'd get in touch with them asap if I were you.
As for travelling with type 1, the following article has some great advice:
https://jdrf.org.uk/living-with-type-1/everyday-life/travelling/
Have a enjoyable time and stay safe.