Hi Jonny,
I posted an identicle post to yours 6 months ago, but via advice through these forums and others Im now getting well on top of things and starting to have a much greater understanding of my Diabetes.
Im on the same insulin regime as yours and I have tackled thigs in the following order.
1) Make sure your lantus dose is correct and working as best it should be, gain an understanding of what it should be doing as if its not then you will be chasing your tail over and over again. Do this via basal testing.
2) Learn how to carb count. Now youve gained a steady platform through your Lantus, carb counting as others have suggested is vital to your novarapid dosage.
3) Work out your own insulin to carbohydrate ratios throughout different times of day.
4) Work out what different types of foods do to you through post mel testing, and compile a simple list of foods which keep you in the safe zone.
Ive followed these steps over the last few months, all down to different bits and peices of advice through the forums and Ive cut my hba1c down to 6.4 and hope to be better next time.