I believe DEC UK based would net around £5000-£5500 per month after tax & pension deductions. If you are a contractor expect something similar.
UK bases are available but in Ryanair land you never know where you'll end up. You may be in luck as they need you and you have a (small amount of) negotiating power.
I think all UK bases are 5/4. In Euroland some bases are 5/3 and the pay varies but expect net around €5000-€5500. The UK contracts are worth considerably more.
Nothing is ever clear until you actually start and even then very little is 100% certain. Good luck!