surbab, congratulations with the result!
It is a decent score and is certainly competitive enough score for any 1 year FT MBA program in the UK.
Having said that, if you strongly believe that with a month of prep you can score better, may be it is worth it - esp, that timing seems to have been your main problem.
If you are only considering 1 year MBAs, you should consider INSEAD , as well. It is the only 1 year program that is in the top 10 b-schools in the world (according to FT ranking)
If you clarify your backgroud a bit and where you stand in the GMAT scoring potential "curve", club members should be able to provide more useful feedback.
But the bottom line is, you should not have an issue even with your current score.
All the best!