Hi Paul,
Welcome to Rootschat

The first question that usually arise for Immigrants, is "were they naturalised ??
See Topic: RootsChat Topics - Naturalisation and Internment
http://www.rootschat.com/forum/index.php/topic,157691.0.htmlfor various topics about what you might find on nat. papers at the TNA, and links for how to find them.
I had a quick look at the TNA (The National Archives) site and found:
Risi, Pasquale Anthony, from Italy. Resident in Kingston-upon-Hull. 1908
Risi, Vincenzo (known as Vincent Risi), from Italy. Resident in Kingston-upon-Hull. 1919
Risi, Angelo, from Italy. Resident in Wolverhampton. 1929
Risi, Antonio, from Italy. Resident in Wolverhampton. 1930
Risi, Vincenzo, from Italy. Resident in Reading. 1931.
Could any of these be the children of your Lorenzo and Geltruda ??
Or could the first two be brothers or cousins. Many immigrants tended to "flock together" in the new country.
good luck,
Bob