We have been assured by our local accountant that, since we have no Italian income, we do not have to pay any tax here.
I think she is wrong - we sold our UK house and I took early retirement, paid monthly into our English bank, so we have money in the bank from the house sale and an income.
Do I need to look for a more qualified accountant, or is she correct?

I think you need a better accountant.

This is the key point...

I received the same advice. Since you only arrived in Italy in July 2017 you would probably only owe tax for 2018. I would start preparing your documentation now and look for an accountant in September when they get back from their holidays. There is not much of a fine for late payment. Ask the accountant what their hourly rate is.

Thanks all for the help.

Are you in a town of less than 20,000 inhabitants in the south of Italy? - if so you may qualify for a special low "flat tax" for foreign pensioners who transfer there.
https://quifinanza.it/pensioni/pensi...italia/279477/

Good thing about this is that it covers Abruzzo, but you still would need to be getting over 22000 to be better off than having a UK allowance