For those in the States, O’Reilly auto parts sells and also rents this socket which would save money for a tool that is only used twice in ones’ lifetime!
Use it much more than that, well worth owning, rather than drive back & forth to shop
3/4" Whitworth is the original correct size, and I have a several old spanners and sockets that cost me $1 each. One cranked ring spanner is cut in half by me, and fits right in there. Worth keeping an eye out at market or old tool sales
1-5/16" is a 3/4" drive size normally, Its handy to have 3/4" drive gear for heavy work, but being that bit bigger, is bit harder to fit the socket and ratchet in the limited space