Blood spots on Henry's right shoulder, disappear between scenes.
The IRA terrorists mainly use WW2 vintage MP-40 sub-machine guns. Although Irish terrorists were committing atrocities with these weapons in the 1950s and early 1960s, by the time that this film is set - mid 1970s - Irish-American supporters had been providing them with large quantities of modern American weapons for some years, and they would be more likely to be using Armalites, of which they had been provided several thousand the Irish-American supporters or AK-47s supplied by Libya, than heavy, unreliable, and elderly WW2 antiques.
In the final street scene where Tempest is shot, there are 20mph speed limit signs on either side of the road. 20mph zones in London were not common before the 2020's, and unheard of in 1975.