Hello, it shouldn't be too tricky. You need to contact ENAC (the Italian national aviation authority, equivalent to the CAA in the UK) and request a certificate of deregistration and pay the fee to request it (if i remember correctly it is approx 70 euros). Once you fill in the form you receive from ENAC the aircraft will not be registered anymore in Italy and you will have to contact the relevant aviation authority requesting a new cert. registration, in your case the CAA.
In order to reduce burocracy steps I suggest that you de-register the aircraft with ENAC without changing ownership, as you will indicate the new ownership when u register it with the CAA in the same form you request for the new cert. reg.
No sense or need to involve a law firm, it is quite straight forward.
The only problem you might find is that ENAC employees aren't known for their excellent English! But you can always ask for further assistance from the CAA (the email is
[email protected])
Should you need any more help let me know!!