SoftUK are selling "Stranglehold" for the PC for £9.99.
Enter the code "Cheap Games" (without quotes) to get free delivery.
You can get cashback on this through certain sites (e.g. 2% Free Fivers, making it £9.79). You can also get £0.51 payback if you are a SoftUK Collector.
Next best price seems to be £12.99 from Play