My brother was in Ipswich most of the day, he saw them fly over last year, but not this year.
And from the Google group im in i got some info that only the Red Arrows formed up near Ipswich and the rest of the formation at southwold.
Also for single engined helicopters it wouldn't be that difficult to do an autorotation landing, their must be loads of space around Buckingham palace, or maybe even the courtyard