Reading is a good half well organised, generally quick, well supported round the course and a good stadium finish
Downsides are that it is a narrow start and there's a sharp hill at two miles which means it can take a while to get into a rhythm. The last two miles are rather dull down a dual carriageway and just when you think you are going to finish you are directed down into an office park for 1/2 mile.
Getting out of the official car parks around the venue can be horrendous; best pick the car parks further away.
OK that's a simplistic generalisation but try and run quicker for shorter distances. This is why people get quicker when they join a club as a coach will include higher speed "repetitions" into training sessions. Really difficult on your own.
As you are getting quicker as you run I have a feeling that you are not in the first flush of youth; if I'm wrong then sorry
What's your flexibility like? Increase your flexibility and your stride length may increase; only a 1-2 cm increase in stride length makes a difference.