While certain processes like AIRE registration are identical regardless of where you may be located there are specific issues that affect consular services in Britain.
There are two main consular offices (and more honorary ones) as follows:
A new office has recently been opened in Manchester too but they do not yet have an official website
The Italian consulate in London is very busy. There are currently very lengthy delays in obtaining passports, ranging from a minimum of 4 months up to 8. The Foreign Office in Rome (Farnesina) has recently allocated more funds to employ more staff but this isn’t an immediate fix. You should be prepared to wait a long time to obtain an appointment. For this purpose you should be using the online service, however, many have reported to us that it is easier to get an appointment by ringing early in the morning, but with a waiting time of up to two hours or more before reaching an operator.
On arrival on appointment day, there are strict security controls and several parallel queues, so you must make sure you are located in the right one too. Security procedures can take up to 10 minutes but queues can be long and you may be waiting outside (rain or sunshine) for a while before going through security and eventually being allowed inside.
If you live near an Honorary Consulate you may consider that route instead and you will find the links on how to reach those representatives here. That list is maintained by the London Comites.