Hi JulieVenice
I am not an expert but, the first question that springs to mind is: are you paying income tax in the UK on your earnings there? If the UK publications pay you in pounds into a British bank account you would not have to pay income tax here as you are paying it in the UK. However, if you are not paying income tax in the UK you can pay income tax here on foreign earnings.
If you intent to write for Italian publications you would need to get a Partita IVA so you can issue invoices, pay tax and claim it back if necessary. I don't know about charging UK publications 20% VAT!
The best thing you can do is find a commercialista (accountant) who can advise you on what you have to do.
Maybe someone here can recommend one.
Good luck