If memory serves me correctly Orange Sim only deals are around £15 a month for an 18 month contract.
Depends on the deal you want:
Canary 15 (£15) if taken as a month to month contract gives you 200mins and unlimited texts.
If you take an 18m you get 300min and unlimited texts
If you take the Canary 10 sim (£10) on an 18m contract you get 200min and unlimited texts
Racoon 15 (£15) is a month to month contract and gives you 300mins and 100texts
Everything else is £20 or above so over what you want to spend.