It really depends on your situation (as you obviously don't receive a means-tested tax credit for working parents if you're not a working parent for example 
), but this is the graph:
The purple line is the average marginal tax rate, the other 2 lines are the 5th percentile and the 95th percentile. The marginal tax rate for people earning between 10 and 20k is quite low because of the labour tax credit which phases in between 10k and 20k. But if you get beyond that the marginal rate gets really high in some circumstances. And if your income gets really high your marginal tax rate basically is 52% because all means-tested tax credits/benefits are fully phased out or fully phased in (except for some very weird cases I suppose?).
Yikes. I see circumstances where one's effective marginal tax rate is greater than 110%! They should at least reform that. Earning 100 Euros and ending up with -10 is a farce.
