There are plans for people already doing the distance, or thereabouts, but you won't find them under beginner plans. They're generally aimed at more experienced runners. For instance, I'm following Greg McMillan's 10k plan for 4-5 runs per week and my longest run in the first week was just over 9 miles.
Are you following a plan at the moment? You could, for example, do the last 6 weeks of the program twice. This would include taper weeks to avoid burnout and you would start building again after 6 weeks. Though if you can knock out 13 miles in 2 hours as a long slow run, you should be able to nail 1:50 in a race.
8 miles yeasterday with Delamere parkrun at 10k effort. Came in at 21:34. Would have been close to a course pb if it weren't for a shoelace tie with 500m to go! Had a great realxed sprint finish so reasonably happy that it was 10k effort and not all out.
More miles in the bag Alehouse. One day I'll make it across to Marple!
DT - two reasons. One is for the running club at school, 20 mins per week trying to keep some brilliant runners happy and cater for a few who just want a bit of fitness. Also our club has no coaches and we're finally sorting ourselves out, elections, AGM etc and realising that we may want some coaches, if only to cover one session a week on a rota basis.