I got a low-ish score for 2014 entry, but decided to apply anyway. I didn't get anywhere as that was a year everyone else did really well on the UKCAT!
It's difficult to assess without seeing how everyone else taking the test has done, but your average is definitely on the low side and the universities that use it tend to do so quite stringently.
The GAMSAT can be sat in September, and you can register until the end of July. It is expensive and from what I've heard takes a lot of work.
There's also the BMAT which Oxford use.
I think Bristol don't ask for entrance exams, but they want AAB at A-Level.