Astronut, heres the ryan scheme as it applies @ Stn (different details @ diff bases but monthly money works out abt the same).
Duty of up to 5 hrs; £45
7 hrs; £130
over 7 hrs; £185
The good news is that these amounts are paid net of tax (company pays the tax) and is received in a personal chq & end of each month. My sector chq for april (normal month as f.o.)was £2100,which was on top of salary. We work hard but sctor chq at month end sure helps my spirits.