The Gov.UK website offers clear information on how to proceed on getting married abroad, country by country. You can even find a tool there that asks you just the right questions to find out exactly what papers you will (probably) need. Having said that, always check the latest requirements with the Italian officials though, or get in touch with your wedding planner for more information. Regulations are known to change, especially in Italy.
As I mentioned in the previous post, official documents in Italy have a validity of 6 months, so bear your wedding date in in mind when you start the process. Another thing I can't underline enough is to always make sure the documents state your full name, the way it is on your passport (see what I did there!). It is normal for us non-Italians to not use our middle name or possibly abbreviate it, but this will cause you trouble in Italy, so make sure the name is written in full. Always.
Here are the steps you will need to take to marry in Italy, if you are a British citizen permanently living in the UK, marrying another British citizen:
- Certificate of No Impediment (CNI). Both you and your partner will have to get a CNI, which you can normally get by giving a notice of marriage at your local register office or registrar in the UK. Note that a Scottish CNI is valid only for 3 months! You will have a wait a period of time for this document to be released, so do not leave it until the last moment.
- The Statutory Declaration. While you are waiting for your CNI to go through, you can get started on making a statutory declaration before a solicitor or public notary in the UK. You can download a template for it here. It's not complicated, but you will absolutely need it in Italy, so don't skip this step. Not that you should skip any of these steps, really. You will be charged a fee for it, so it might be worth asking a few different offices for the prices.
- Legalisation. Once you have both your documents you will have to get them legalised by the legalisation office. You can find out how and where to do this by clicking here. At the moment I'm writing this, the price is £30 per document + postage.
- Translation. You will then need to get your CNI officially translated into Italian. It has to be done by an official translator in Italy, you can find a list here, or ask your wedding planner to help you out with this.
Also note that if you're a woman and you have been divorced/widowed less than 300 days, you will not be able to marry without a medical certificate and a legal waiver. This part of the procedure is same for all, so you can see how to do this from the Getting Married in Italy - US edition, or send me a message and I'll get you on the right track.