Confused......so am I !
The taxation system across the EU is confused with the term Social tax being the most variable. In the UK social tax is called National Insurance and is generally to provide old age pension, unemployment protection Etc.
Income tax goes to the govenment for most of the other stuff.
The total of both of these is likely to be IRO 40% for your average pilot.
There is also a local property tax that the local authorities use to pay for local services, these you pay out of taxed income and depend on the size of your house.
I hope this helps give a general picture of the UK tax system but please if you work out of the UK get professional advice !!!!