New Runner - 5k/10k

been running for a few months trying to lose weight, started off on couch to 5k programme, my pace was around 10-11 mins per mile & is now between 8-9 mins per mile.

what is a good time for 5k/10k?

A good time is whatever you can achieve 

Its impossible to tell without knowing age, fitness level, body weight, training level, how long you have been training etc ... etc ...

If you can maintain 8 - 9 min/mile pace over the distance, you won't be the slowest runner in a 5k or 10k, but you won't be contesting for the top three places.

Best thing to do is participate in a race so that you have a Personal Best set under race conditions and over an official distance.  This will then give you a target to beat over the next few years as your running improves.

true...my main aim when I started running was to lose weight, which I have done. However, I enjoy running and want to start doing more races, I did a 5k in July this year & since then have shaved 3 minutes off my finishing time (so far)

I fancy running a 10k in the near future to test myself!

8-9min mile pace.

Few more months and a few pounds less and you'll be flying.