Tenerife marathon. November

Good evening. I am new here.
Have been running for around a year.
Building from 5k to 10k and and a half marathon in April this year.
Since then i have done another 2 halves, and have now committed to the full marathon.

I have been working through the bupa intermediate plan for marathon training and up to now has been going well.

Ultimately am aiming for a sub 4 hr, but read that most strive for this and fail.

My recent halves have been a 1.49 and a 1.52. 

10k at 48.30

I am due at the Manchester 1/2 marathon in October.

Any advice? 
What should i be doing, is the plan efficient enough?

One other question. On the plan it states 40 min interval training. Would you think this includes the 5 mins warm up and cool down. Or should i add these to the 40 mins.

Any pointers appreciated.
Am just north of 40 yrs old

Never understood the buzz of running, until now

Cheers