My current contract with them is 400 minutes and 1500 texts a month for £44 but im normally paying between £60 and £100 as im always over my tariff.
What causes you to go over each month? Calls, texts, data? The answer will affect which contract is best for you.
Just picking a few at random,
O2 Online 40 1200m/1000txt 24mth@£39 free 6600
Voda 1200m/ultd txt 12mth@£50 free E71
Orange Dolphin 40 900m/ultd txt 18mth@£34 free 6500, E71, etc.
With your spend level, a call to Orange asking for your PAC should get you through to retentions who I would expect to offer a pretty keen deal on Dolphin 40 to hang on to your business.
HTH.