I am training a New rider and I had just progressively made the rides a bit harder. He has been going out in the evenings in the week for 10 mile rides on his own- but after a couple of weeks I took him on a 20 miler- Next week 25 with a hill. Next week 30 with a bit of up and down and last week it was 40 miles on the flat with a bit of speed occasionally. Next week I am going to kill him as he will do a 30 miler with a few steep longer climbs.

But last time he was on a bike was 30 years ago. In 6 weeks he has progressed upwards. Only one long ride at the weekends---That has progressively got harder--- and he does the 10 milers twice a week on his own.

So looking at your monthly milage- you are coming on well. Look around for an organised ride in your area and do a milage that will just stretch you a bit. Don't attempt anything that will knock your confidence but look for a 25 to 35 miler to just show yourself what you can do. I reckon you are ready for it.