Brathay Half Marathon

So today thanks to my son not believing I can run 13.1 miles I signed up to the inaugural Brathay Half Marathon! Only after I had paid did I discover what the elevation is:

Eek! So I have downloaded a half marathon training programme and now to steadily build up from being able to run 6 miles (I have 2 x 10k races in December) to reach 13.1 miles by May 22nd..

Any tips or advice is welcome!