Chanice - basil will never be happy outdoors here in late Spetember - it's not hot enough and not bright enough. Plus we don't have sufficient light indoors in the winter here for Basil to thrive. It needs high heat and a lot of light to be happy. I don't even put mine outside in the summer but grow it in my greenhouse for more reliable heat. Basically basil needs to be treated as an annual and resown next year.

I'd put it in the brightest spot you can find and take every picking as a bonus.

I would also check under the pot for any bugs. It looks as if yours might be being nibbled by something.

yeah i bought the basil in a few weeks ago now... do you have any idea why some leaves are big and some are small... this has only just started happening..

also is there anything i can do to help it.. ie should i prune it back and hope it grows again or just wait it out and see what happens

The small leaves just mean it's not happy. Don't prune it. It needs all its leaves to photosynthesise. Give it all the light you can. A drop of fertiliser in its water next time you give it a drink might help. But basically you are trying to work against nature. Basil just doesn't like being inside - unless you have grow lights and heaters like commercial growers.

Did you buy it in the herb section of a proper garden centre was is it from a supermarket?

it was from homebase garden centre... i got it around may and all summer its had small leaves and been growing fine.. only now its gone big ones lol

OK I was just checking it was intended for growing on unlike the ones from the veg section of the supermarket which are short term for kitchen use having been forced on.

Basically we are getting close to the limit for basil in our climate. Mine is still fine but it's been under glass all its life. It will start to deteriorate as the light levels go down and the temperature goes down.