HI Welly
the SAP Notes to look at are 1933498 & 2211016.These give you the NetWeaver release & support pack mapping between the UI Add-on version on Gateway & the SAPUI5 version.
To upgrade a major version eg from 1.22 to 1.24 you must load the correct UI Add-on. To upgrade above 1.28 you also need to upgrade to UI Add-on 2.0 on Netweaver 7.50.
To upgrade the minor SAPUI5 version eg from 1.28.1 to 1.28.12 follow the instructions in note 2118663.
THe other note to watch is 2217489 which is the central note for the maintenance & update strategy of UI Add-on
Good luck
Jocelyn